Editing Base rate fallacy (section)

===O. J. Simpson trial===
{{see also|O. J. Simpson murder trial}}

[[O. J. Simpson]] was tried and acquitted in 1995 for the murders of his ex-wife Nicole Brown Simpson and her friend Ronald Goldman.

Crime scene blood matched Simpson's with characteristics shared by 1 in 400 people. However, the defense argued that the number of people from Los Angeles matching the sample could fill a football stadium and that the figure of 1 in 400 was useless.<ref>Robertson, B., & Vignaux, G. A. (1995). '' Interpreting evidence: Evaluating forensic evidence in the courtroom. '' Chichester: John Wiley and Sons.</ref><ref>Rossmo, D. Kim (2009). '' Criminal Investigative Failures. '' CRC Press Taylor & Francis Group.</ref> It would have been incorrect, and an example of prosecutor's fallacy, to rely solely on the "1 in 400" figure to deduce that a given person matching the sample would be likely to be the culprit.

[[File:OJ Simpson case frequency tree.svg|thumb|Frequency tree of 100 000 battered American women showing the base rate fallacy made by the defense in the [[O. J. Simpson murder trial]]]]

In the same trial, the prosecution presented evidence that Simpson had been violent toward his wife. The defense argued that there was only one woman murdered for every 2500 women who were subjected to spousal abuse, and that any history of Simpson being violent toward his wife was irrelevant to the trial. However, the reasoning behind the defense's calculation was fallacious. According to author [[Gerd Gigerenzer]], the correct probability requires additional context: Simpson's wife had not only been subjected to domestic violence, but rather subjected to domestic violence (by Simpson) {{em|and}} killed (by someone). Gigerenzer writes "the chances that a batterer actually murdered his partner, given that she has been killed, is about 8 in 9 or approximately 90%".<ref>Gigerenzer, G., Reckoning with Risk: Learning to Live with Uncertainty, Penguin, (2003)</ref> While most cases of spousal abuse do not end in murder, most cases of murder where there is a history of spousal abuse were committed by the spouse.