tag:theconversation.com,2011:/us/topics/oj-simpson-26090/articlesOJ Simpson – The Conversation2017-08-28T20:08:30Ztag:theconversation.com,2011:article/822502017-08-28T20:08:30Z2017-08-28T20:08:30ZFrom the crime scene to the courtroom: the journey of a DNA sample<p>The O.J. Simpson murder trial in 1995 introduced DNA forensics to the public. The case collapsed, partly because the defence lawyers cast doubt on the validity of the evidence thanks to the inappropriate way the samples <a href="http://www.latimes.com/opinion/op-ed/la-oe-0618-morrison-scheck-oj-simpson-20140618-column.html">were handled</a>. </p>
<p>Things have changed since then. There are now safeguards in place to ensure the integrity of the chain of evidence. Laboratory protocols and procedures have also advanced. </p>
<p>By following a piece of evidence from the crime scene to the courtroom, we’ll explain just how DNA is studied in the lab and used in the modern legal system.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/explainer-forensic-science-2817">Explainer: Forensic science</a>
</strong>
</em>
</p>
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<h2>From the crime scene</h2>
<p>The DNA sample’s journey begins at the crime scene.</p>
<p>There are <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4637504/#B63">several principles</a> that guide DNA evidence collection by the <a href="http://www.abc.net.au/news/2015-08-16/crime-scene-investigation-specialists-reveal-gritty-side-of-jobs/6681316">crime scene examiner</a>. In particular, the avoidance of contamination or DNA degradation, and ensuring the chain of custody. </p>
<p>The risk of contamination (from the collector or other evidence samples) is reduced by using sterile, disposable supplies. Degradation is minimised by drying samples before bagging. </p>
<p>Storing dried samples in <a href="https://www.mcscs.jus.gov.on.ca/english/centre_forensic/InformationforInvestigatorsSubmitters/HandbookofForensicEvidencefortheInvestigator/CFS_handbook.html">paper bags</a> rather than plastic, and maintaining samples at the proper temperature helps preserve the DNA and prevent microbial contamination. </p>
<p>It is also important to plan what to collect and how – sufficient material may be required for independent testing by the defence. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/183541/original/file-20170828-27540-5oq4kn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/183541/original/file-20170828-27540-5oq4kn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=320&fit=crop&dpr=1 600w, https://images.theconversation.com/files/183541/original/file-20170828-27540-5oq4kn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=320&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/183541/original/file-20170828-27540-5oq4kn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=320&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/183541/original/file-20170828-27540-5oq4kn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=402&fit=crop&dpr=1 754w, https://images.theconversation.com/files/183541/original/file-20170828-27540-5oq4kn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=402&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/183541/original/file-20170828-27540-5oq4kn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=402&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Police must ensure samples are not contaminated.</span>
<span class="attribution"><span class="source">James Hereward and Caitlin Curtis</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>To the lab</h2>
<p>When any sample arrives in a lab, the first step is to extract the DNA. </p>
<p>The blood samples analysed in the O.J. Simpson trial were typical of the time when large amounts of DNA were required to conduct testing. Today, small amounts of DNA, known as trace DNA, can be analysed from items such as cigarette butts, hair follicles, saliva, semen, and even <a href="http://www.bbc.com/news/world-us-canada-40855915">faeces</a>.</p>
<p>This is possible because of the invention of a method in the 1980s called the polymerase chain reaction or “<a href="https://www.khanacademy.org/science/biology/biotech-dna-technology/dna-sequencing-pcr-electrophoresis/a/polymerase-chain-reaction-pcr">PCR</a>”, which allows an individual strand of DNA to be replicated many times. This creates thousands of copies until there is enough DNA to conduct tests.</p>
<h2>Analysis begins</h2>
<p>The mainstay of modern DNA identification is <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3561883/">short tandem repeat</a> (STR) markers, which are small sections of DNA that vary by length (the number of repeats). </p>
<p>Multiple STR markers are used to create a DNA profile. They are tested using commercial kits that often incorporate a sex determination test (the <a href="https://link.springer.com/article/10.1007%2FBF01371335?LI=true">amelogenin</a> gene). </p>
<p><strong>Mitochondrial DNA</strong></p>
<p>Another method uses mitochondrial DNA.</p>
<p>Mitochondrial DNA tends to last longer than other types of DNA and is often relied on in cold cases. The sequence of mitochondrial DNA “letters” is passed down from mother to child (with the exception of rare mutations), so mothers and grandmothers share the same DNA sequence as their children (but fathers do not). </p>
<p>This makes mitochondrial DNA useful in identifying missing persons - the bones of Daniel Morcombe <a href="https://www.theguardian.com/world/2014/feb/12/daniel-morcombe-case-mothers-dna-matched-100-with-bone-sample">were identified this way</a>. </p>
<hr>
<p><em><strong>Read more</strong> <a href="https://theconversation.com/ned-kelly-remains-are-positively-identified-but-how-was-it-done-3174">Ned Kelly remains are positively identified … but how was it done?</a></em> </p>
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<p><strong>The Y chromosome</strong></p>
<p>The Y chromosome is present only in males and is passed from father to son. This makes Y chromosome STR markers a useful tool in situations such as <a href="http://www.kgw.com/news/crime/how-are-rape-kits-processed/449988969">sexual assault cases</a> where male and female DNA samples might be mixed and the male suspect’s identity needs to be established.</p>
<p>In the same way as mitochondrial markers, Y-markers can be used for identification through family matching. The process of <a href="http://www.latimes.com/local/lanow/la-me-familial-dna-20161023-snap-story.html">familial matching</a> in criminal investigations raises <a href="http://criminal.findlaw.com/criminal-rights/familial-dna-searches.html">privacy concerns</a> but is increasingly commonplace. </p>
<p>In one recent incident, it was suggested that the surname of a suspect was identified from records of male <a href="http://www.azcentral.com/story/news/local/phoenix/2016/11/30/how-forensic-genealogy-led-arrest-phoenix-canal-killer-case-bryan-patrick-miller-dna/94565410/">family members</a> in public genetic ancestry databases. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/183556/original/file-20170828-27807-fdmar0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/183556/original/file-20170828-27807-fdmar0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/183556/original/file-20170828-27807-fdmar0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/183556/original/file-20170828-27807-fdmar0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/183556/original/file-20170828-27807-fdmar0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/183556/original/file-20170828-27807-fdmar0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/183556/original/file-20170828-27807-fdmar0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Tests often look for Y chromosome STR markers to establish identity.</span>
<span class="attribution"><span class="source">University of Michigan School of Natural Resources & Environment</span></span>
</figcaption>
</figure>
<h2>DNA databases and sample matching</h2>
<p>Australian law enforcement uses the National Criminal Investigation DNA Database (<a href="https://www.acic.gov.au/our-services/biometric-matching/national-criminal-investigation-dna-database">NCIDD</a>), which is managed by the Australian Criminal Intelligence Commission.</p>
<p>The more records added to the database, the greater the odds of making an accidental match. This is because the number of potential matches increases.</p>
<p>To reduce the risk of false “hits”, genetic profiles can be made more complex. Increasing the number of STRs in each profile reduces the risk of a spurious match because the probability of a match (at 20 markers, for example) is estimated by multiplying the probabilities of each STR marker. </p>
<p>The Australian system originally used nine STR’s and a sex-determination gene. In 2013 this was increased to <a href="https://www.google.com.au/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&cad=rja&uact=8&ved=0ahUKEwjpjLfGjuLVAhUHnpQKHZ5MAuUQFghIMAQ&url=http%3A%2F%2Fwww.anzpaa.org.au%2FArticleDocuments%2F218%2FDNA%2520Profiling%2520Success%2520Rates%2520ISFG%25202013.pdf.aspx&usg=AFQjCNGQpqd6ZYZrMyKkhZS4KYWsLsmvZA">18 core markers</a>.</p>
<p>Internationally, there are moves towards a standard set of 24 markers (such as <a href="https://www.thermofisher.com/order/catalog/product/4476135">GlobalFiler</a>). With this many markers, the odds of two people having the same profile (twins excepted) are incredibly small. This makes an STR profile a powerful way to exclude suspects as well as making matches. </p>
<h2>In the courtroom</h2>
<p>Modern DNA forensic methods are powerful and sensitive, but great care must be taken to prevent miscarriages of justice. </p>
<p>It is difficult for people to comprehend probabilities like one in a quadrillion, and the presentation of such numbers in court can become prejudicial.</p>
<p>In the case of <em><a href="http://eresources.hcourt.gov.au/showCase/2012/HCA/15">Aytugrul v the Queen</a></em>, DNA evidence was presented as an exclusion percentage of 99.9, and the defence argued that this would indicate certainty of guilt to the jury. </p>
<p>Although the High Court of Australia ultimately allowed the DNA evidence presentation in <em>Aytugrul v the Queen</em>, survey data suggest that the statistical presentation of genetic evidence may affect how it is understood and <a href="http://www.tandfonline.com/doi/abs/10.1080/00450618.2014.992472">used by a jury</a>.</p>
<p>Such issues have lead to <a href="https://www.justice.gov/opa/pr/justice-department-issues-draft-guidance-regarding-expert-testimony-and-lab-reports-forensic">guidelines</a> by the US Department of Justice, among other justice groups, for the language used in forensic testimony and reports.</p>
<p>There’s also a risk that contamination might implicate an innocent person. For that reason, DNA evidence is best used in support of other types of evidence. </p>
<p>In the case of <em><a href="http://guides.sl.nsw.gov.au/c.php?g=671792&p=4729488">R v Jama</a></em>, DNA evidence was the sole basis of the rape case. Only after <a href="http://www.aic.gov.au/media_library/publications/tandi_pdf/tandi506.pdf">16 months’</a> imprisonment was it revealed that the sample taken by the doctor was probably contaminated.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/183562/original/file-20170828-27547-1kkhxr7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/183562/original/file-20170828-27547-1kkhxr7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=500&fit=crop&dpr=1 600w, https://images.theconversation.com/files/183562/original/file-20170828-27547-1kkhxr7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=500&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/183562/original/file-20170828-27547-1kkhxr7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=500&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/183562/original/file-20170828-27547-1kkhxr7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=628&fit=crop&dpr=1 754w, https://images.theconversation.com/files/183562/original/file-20170828-27547-1kkhxr7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=628&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/183562/original/file-20170828-27547-1kkhxr7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=628&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">DNA can now be turned into digital data by massively parallel sequencing machines.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<h2>Forensics in the future</h2>
<p>DNA forensics will continue to evolve.</p>
<p>Take a genetic test that can predict <a href="http://www.fsigenetics.com/article/S1872-4973(12)00181-0/abstract">eye and hair colour</a>: this test examines (or “genotypes”) 24 single letter DNA variants. These are analysed with a statistical model that provides probabilities for hair and eye colour based on a large database that links DNA variants to appearance.</p>
<p>Understanding how DNA is linked to <a href="https://www.newscientist.com/article/mg22129613-600-genetic-mugshot-recreates-faces-from-nothing-but-dna/">facial features</a> has even led to the creation of DNA-based <a href="https://snapshot.parabon-nanolabs.com/">mugshots</a>. </p>
<p><a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3238019/">“Massively parallel” sequencing</a> machines are also a significant advance. These can turn the approximately 3.2 billion DNA “letters” of the human genome into digital information in a matter of hours. </p>
<p>This opens up all of the information contained in our genetic code to law enforcement. For example, some researchers claim it’s possible to <a href="http://www.reuters.com/article/us-dna-suspects-age-idUSKCN0V31BQ">predict the age of a suspect from a blood sample</a> within a mean error margin of 3.8 years, based on methylation markers in the DNA, and this may be improved with the assistance of <a href="http://www.sciencedirect.com/science/article/pii/S1872497317300388">machine learning</a>. </p>
<p>The more we understand the link between appearance and DNA, the better its predictive power will be. It’s tempting to speculate how the O.J. Simpson trial may have turned out with modern forensic DNA protocols and technology.</p><img src="https://counter.theconversation.com/content/82250/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Genetic evidence has become a critical aspect of modern criminal investigations. What are the methods and approaches used in present-day DNA forensics?Caitlin Curtis, Honorary Research Fellow, The University of QueenslandJames Hereward, PostDoc Ecological and Evolutionary Genetics, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/749662017-04-24T23:23:36Z2017-04-24T23:23:36ZHow statistical thinking should shape the courtroom<figure><img src="https://images.theconversation.com/files/165117/original/image-20170412-25870-1loav10.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Courtroom decisions are more like a game of chance than you may think.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/aerust/9590772048/in/photolist-fBvdoL-8TZg4D-8KgHv8-RKz54g-88bgji-naG6kZ-5JepR-ibmNwe-dLLg2u-gVo63P-8mp9i3-jGjqBF-8e1ok9-9t55Nh-pi8Gzm-7TzCHH-d8QgxU-4pi6gm-eUX9oU-96T8Qm-ntMfWZ-dsyum9-9dmrST-jGjARY-8ML8Wg-5dxBST-jGkgrA-7awYgY-dRsLkh-p488VL-bW8nKq-8CFEDj-apeJpP-eSxxYX-kX1S3-8823SL-8N2xDo-4rBUES-huWVPJ-a91URN-9VA9dD-qf7GTa-kMAJoc-riUAU2-7NBY97-9G6iKN-8MPazf-8WcxXs-beguDi-abQbiw">Cropped from aerust/flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>The probabilistic revolution first kicked off in the 1600s, when gamblers realized that estimating the likelihood of an event could give them an edge in games of chance. </p>
<p><a href="http://www.jehps.net/Decembre2007/Denis.pdf">Today</a>, statistics has become the dominant way to communicate scientific findings. But courts can be hesitant to incorporate statistical evidence into decisions. Indeed, they have <a href="http://www.jstor.org/stable/29762778">historically been antagonistic</a> toward probabilities and <a href="http://digitalcommons.law.ou.edu/cgi/viewcontent.cgi?article=1030&context=olr">are loath to be swindled</a> by slippery statistics.</p>
<p>However, as an educator of statistics who has consulted in a variety of contexts and has served as expert witness to the U.S. District Court in Montana, I find that both my experience and my review of the evidence suggest that courts increasingly feature statistical thinking – whether or not it is identified as such. </p>
<p>Society needs to prioritize educating juries in the language of statistics. Otherwise, juries will be forever at the mercy of convincing, yet potentially invalid, testimony. Courtroom decisions should be based on facts and probabilities, not manipulation by a skilled prosecutor or defense attorney.</p>
<h2>Thinking statistically</h2>
<p>Probabilities changed the way human beings thought about outcomes. They are a useful tool for expressing our uncertainty about events in the world. </p>
<p>Will it rain today? It will or it will not, that much is certain. But probability allows us to express our ignorance about whether it will rain and quantify the degree to which we are uncertain. Stating “it will probably rain today” constituted a very innovative and different way of thinking.</p>
<p>Probabilities play a role in our daily lives, in decisions from whether to take an umbrella to work to whether to purchase flood insurance. We can consider “statistical thinking” to be any situation where probabilities are involved. </p>
<p>To some extent, humans are <a href="http://www.cep.ucsb.edu/papers/intuitivestat96.pdf">intuitive statisticians</a>. For instance, research suggests we can revise a belief in the light of new evidence as prescribed by <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4191302/">a statistical theorem</a>, if the probabilities are given in a relatively intuitive rather than abstract fashion.</p>
<p>Statistical reasoning pervades many of the conclusions we draw regarding scientific phenomena. Even physics has had to acknowledge the <a href="http://pages.physics.cornell.edu/%7Esethna/StatMech/EntropyOrderParametersComplexity.pdf">reality of probabilities</a>. So, if the courts use scientific findings as evidence, probabilities should naturally make their way into courtroom decisions. </p>
<h2>Evaluating the evidence</h2>
<p>If juries do not understand the nature of statistical conclusions, then they will be tempted to believe that scientific evidence is conclusive and deterministic, rather than probabilistic. For example, probabilities show us that cigarette smoking does not necessarily lead to cancer. Rather, extensive nicotine addiction likely leads to cancer. </p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/166296/original/file-20170421-24654-1mrixen.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/166296/original/file-20170421-24654-1mrixen.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/166296/original/file-20170421-24654-1mrixen.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/166296/original/file-20170421-24654-1mrixen.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/166296/original/file-20170421-24654-1mrixen.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/166296/original/file-20170421-24654-1mrixen.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/166296/original/file-20170421-24654-1mrixen.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Heads or tails?</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/armydre2008/7058346583/in/photolist-qC9VZg-6AYQ6N-bKHSwK-cyb52A-7GwwR1-SuYMJt-39KX5x-51xRTp-4WKWib-rJ7Tqd-9ygQ3c-9L5cX7-e3HWUu-cDH1MG-EibHGN-9vGn5b-5kTk3F-omfc1-68VZe7-kHSQB-pVyexg-3i4WAy-aonY7z-bD2FVv-5TAxNN-q2jJMq-TnJToe-aP6TBx-6Pfu6F-AaGXpT-TsXWbc-dV7Pr6-aPjMnT-9UFF7K-aDiVvm-eTQCvn-dYvPAB-8KNnAU-4N8oqY-GQ6DaU-aGn1K2-dTMZnL-aTZxti-3f8Dad-6MyMLv-6vBswW-nJkL3-eWqS9S-2KRUo9-dy8fV3">armydre2008/flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Evidence can only fit a theory probabilistically. If we flip a coin 10 times and get 10 heads in a row, that suggests the coin may not be fair, but does not “prove” that it is biased. </p>
<p>Consider the analysis of DNA found at the crime scene. Is the DNA that of the accused? Maybe. Not definitively. A statistician might say, “The probability of this degree of DNA match occurring by chance is extremely small. The match may be due to chance, but since this probability is so small, we may conclude that it likely did not occur by chance, and use it as evidence against the accused.” </p>
<p>Of course, human judgment is fickle. Until jurors are trained to make rational decisions based on facts and probabilities, they will continue to be easily swayed by <a href="http://www.thejuryexpert.com/2010/07/persuading-with-probability-the-prosecution-of-o-j-simpson/">convincing litigators</a>.</p>
<p>In the 1995 trial of OJ Simpson, for example, the bloody gloves found at the crime scene constituted powerful evidence against the accused. The samples obtained were extremely likely to belong to the defendant. </p>
<p><a href="http://www.thejuryexpert.com/2010/07/persuading-with-probability-the-prosecution-of-o-j-simpson/">A statistically educated jury</a> would not fall for Johnnie Cochran’s classic defense: “If it does not fit, you must acquit.” They would know in advance that no evidence, whatever the kind, fits a theory perfectly.</p>
<p>Cochran’s statement was, statistically speaking, utter nonsense. Of course no model fits perfectly, but which is the more probable model? That’s the task jurors ultimately face, even if they often perceive it as a “guilt” versus “no guilt” decision. </p>
<p>Whenever courts work with DNA matches, they must incorporate acceptable risk and error. But if such uncertainty can be quantified accurately, then it can serve as an aid in decision-making.</p>
<p>Statistical thinking indeed plays a role in the decision between guilt and innocence in a criminal trial. When a jury renders a “guilty” verdict, there is always the chance that the accused is not guilty, but that the many circumstances of the case simply lined up against him or her to lead the jury to a guilty verdict. In other words, the probability of the observed evidence under the assumption of innocence is so low that the evidence likely occurred under a more probable “narrative” – that of guilt. </p>
<p>But, when we make such a decision, we do so with a risk of error. This could be quite devastating to a defendant falsely put to death when all along he or she was innocent. For example, when researchers applied DNA testing to death row inmates in Illinois, they found that <a href="http://forensicoutreach.com/library/5-real-life-cases-where-dna-profiling-changed-everything/">the results exonerated</a> several inmates.</p>
<p>Errors in probability-based decisions can indeed be costly. Without a grasp of how virtually all decisions are based on probabilistic thinking, no jury can be expected to adequately assess any evidence in a rational way.</p>
<h2>Base rates</h2>
<p>Courts also struggle with whether and how to use base rates, another type of statistical tool. </p>
<p>A base rate is the probability of some characteristic being present in the population. For instance, say an individual takes a diagnostic test for a disease, such as HIV. The probability that she has the disease would be higher if she were sampled from a high-risk group – for example, if she shares needles to support a drug addiction, or engages in promiscuous sex with risky partners.</p>
<p>Courts often ignore base rate information. In <a href="http://law.justia.com/cases/wyoming/supreme-court/1989/122160.html">Stephens v. State</a> in 1989, the Wyoming Supreme Court heard testimony that “80 to 85 percent of child sexual abuse is committed by a close relative of the child.” They ultimately dismissed this, concluding that it was difficult to understand how statistical information would help reach a decision in an individual case. </p>
<p>In another case, a <a href="http://law.justia.com/cases/minnesota/supreme-court/1994/c3-93-381-2.html">justice of the Minnesota Supreme Court proclaimed</a> that she was “at a loss to understand” how base rates could help predict whether a particular person posed a danger to the public. </p>
<p>Part of the problem is that this information can appear biased against the accused. For instance, consider again the defendant accused of child sexual abuse. The probability that he is guilty might be evaluated in light of the fact that most perpetrators of abuse are relatives of or closely related to the family. This could be interpreted as biasing the evaluation against the accused. However, the courts have considered base rates in employment discrimination cases, an area where perhaps this information seems more naturally relevant (for example, <a href="http://caselaw.findlaw.com/us-supreme-court/433/299.html">Hazelwood School District v. United States</a>). </p>
<p>If the courts are willing to use base rate information in discrimination cases, they should be encouraged to consider them in other cases as well, even if they seem less intuitive. </p>
<h2>Learning to think statistically</h2>
<p>Courts should make it a priority to instruct juries on how to interpret probabilistic evidence, so that they are not at the mercy of a convincing, yet potentially misleading, prosecutor or expert witness.</p>
<p>For example, juries might learn elementary statistics through <a href="http://www.thejuryexpert.com/2010/07/persuading-with-probability-the-prosecution-of-o-j-simpson/">coin-flipping lessons</a>. This could help them, at minimum, find a way to think about the usual “beyond a reasonable doubt” instruction in a criminal trial. </p>
<p>When the assumption of innocence is rejected in favor of guilt, one does so with a risk of being wrong. How much risk is a jury willing to tolerate? Five percent? One percent? Surely such risk must also depend on the severity of the proposed punishment. Every decision is an exercise in risk and cost benefit analysis. </p>
<p>Until juries <a href="http://scholarlycommons.law.northwestern.edu/cgi/viewcontent.cgi?article=1140&context=facultyworkingpapers">learn elements of statistical thinking</a>, they are likely to continue making verdict decisions without the appropriate framework in mind. Probabilities have taken over the world, and this fact needs to be recognized by the courts.</p><img src="https://counter.theconversation.com/content/74966/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Daniel J. Denis does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>We live in a probabilistic world. The courts need to catch up – and start training juries in statistics.Daniel J. Denis, Associate Professor of Quantitative Psychology, University of MontanaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/568392016-03-29T10:12:36Z2016-03-29T10:12:36ZWhy we need cameras in court<figure><img src="https://images.theconversation.com/files/116417/original/image-20160324-17835-1osbk05.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Smile: you're on camera.</span> <span class="attribution"><span class="source">Maxim Tarasyugin/Shutterstock</span></span></figcaption></figure><p>New BBC Two drama <a href="http://www.bbc.co.uk/programmes/b071cm1b">The People v OJ Simpson</a>, starring John Travolta and Cuba Gooding Jr, is a stark reminder of how cameras in courts can turn a murder trial into a real-life TV soap opera.</p>
<p>A little over 20 years ago, the world was gripped – and watched intently – as every microscopic detail of American superstar <a href="http://www.latimes.com/local/la-oj-simpson-stories-storygallery.html">OJ Simpson’s prosecution</a> for double murder was played out over 10 months in a Los Angeles court room.</p>
<p>Simpson’s lawyer <a href="http://www.biography.com/people/robert-shapiro-121715">Robert Shapiro</a>, played by Travolta in the current Monday night series depicting the case, shot to prominence alongside a PR-hungry cast, including fellow defence solicitor <a href="http://www.biography.com/people/robert-kardashian-010716">Robert Kardashian</a> – the father of the oh-so-famous Kardashian clan we endure today.</p>
<p>The circus that surrounded the media’s proclaimed “<a href="http://www.imdb.com/title/tt3715212/">trial of the century</a>” set back campaigners’ hopes of filming in English and Welsh crown courts by at least a decade, according to high profile camera supporters such as former lawyer and BBC legal correspondent <a href="http://www.rozenberg.net/">Joshua Rozenberg</a>.</p>
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<figcaption><span class="caption">Will allowing TV cameras in court be an important step for open justice?</span></figcaption>
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<p>Meanwhile, staunch opponents of cameras in courts, such as Labour peer Helena Kennedy QC, have used the OJ Simpson trial to show how the TV business would simply chase revenue and ratings by seeking the “<a href="http://www.theguardian.com/commentisfree/2013/nov/03/cameras-in-court-threat-justice">salacious and sensational</a>”, rather than improving the public’s understanding of the system.</p>
<p>Either way, it seems the time has come. Last week, justice minister Shailesh Vara <a href="http://gu.com/p/4hytd?CMP=Share_iOSApp_Other">announced</a> that cameras will be allowed for the first time in eight crown courts in England and Wales. </p>
<h2>Trial by TV?</h2>
<p>The <a href="http://www.huffingtonpost.co.uk/entry/tv-cameras-to-be-allowed-into-crown-courts-for-first-time-in-pilot-scheme_uk_56eeaa2ce4b0fbd4fe080dda">pilot scheme</a> will mean that only senior judges’ sentencing remarks can be filmed. Filming of all other court participants, including staff, victims, witnesses, defendants, barristers and solicitors will remain expressly forbidden.</p>
<p>In reality, it’s likely that all this will mean is that TV reporters will be able to cut to a short clip of the judge, rather than reading their key quotes from a notepad in a piece to camera. </p>
<p>But Vara’s hope is also for greater “transparency” as the public will “see and hear the judge’s decision in their own words”. And surely he has a point. As my first local newspaper editor told me as I headed to court for the first time to cover a case as a trainee reporter, “not only must justice be done, it must also be seen to be done”. So why not allow the viewer to see for themselves?</p>
<p>As <a href="http://www.mansfieldchambers.co.uk/">Michael Mansfield QC</a> also points out, “justice is supposed to be public”. Although anyone can walk into a public gallery at court, he believes “that doesn’t reach a wide enough audience and we’re also subject to the editorial delights of various newspapers as to what they want to report”.</p>
<p>But hang on. Helena Kennedy does make an <a href="http://www.bargatemurray.com/behind-the-closed-door-the-administration-of-justice-brought-to-you-by-sky-news-and-the-bbc/">impassioned and compelling counter-argument</a>. She argues that TV exposure will put off witnesses, discourage victims even if their faces are not on screen, and distort the behaviour of lawyers and judges.</p>
<p>“The public and press galleries enable members of the public, families and friends of those involved, and the media to witness what takes place and ensure fair play,” she says. </p>
<p>“Transparency does not mean the whole country has to see highlights like the goals in a football match. Justice is a very important part of our democracy and we have to handle it with care.”</p>
<p>There is an eloquent case on sides but surely the central question surrounds the level of access? The latest proposal is very limited. Only if the rules are relaxed much further would Kennedy’s fears of voyeurism and TV miscreants running amok become anywhere near a reality.</p>
<p>Of course, cameras in UK courts is actually nothing new. Scottish broadcasters have been allowed to <a href="http://www.scotland-judiciary.org.uk/24/944/Review-into-cameras-in-court">televise courts</a> under restrictions since 1992, but it rarely happens.</p>
<p>And how many of Britain’s 65m citizens will recall that in 2011 then Justice Secretary Ken Clarke allowed <a href="http://www.theguardian.com/law/2011/sep/06/ban-filming-courts-to-be-lifted">judges’ sentencing remarks to be filmed</a> in the appeal courts in England and Wales? Very few, I’d imagine – and that’s precisely because it has not led to the saturated and salacious coverage Kennedy predicts.</p>
<p>It’s fair to say that while we don’t want a repeat of the OJ trial, we should have transparency – and so from here on, it’s going to be about getting the balance just right.</p><img src="https://counter.theconversation.com/content/56839/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>TV cameras will be coming to a court near you.Paul Broster, Director of Journalism, University of SalfordCaroline Cheetham, Lecturer and Visiting Fellow in Journalism, University of SalfordLicensed as Creative Commons – attribution, no derivatives.