Hirophysics com The Use of Bayesian Statistics in

Hirophysics. com The Use of Bayesian Statistics in Court By: Nick Emerick 5/4/11

Hirophysics. com Bayesian vs. Frequentist § Where the frequentist estimates what an answer could be bayesian states the answer is unknown without further information. § Bayesians consider probability statements to be a degree of “personal belief” (prior probability) when not all of the factors are known. § Example: 99. 5% of faulty computer parts run over 50 o. F § A part runs at 55 o. F, how like is that part to be faulty? § Frequentist- not enough information § Bayesian- more accurate prediction with the prior probability

Hirophysics. com The Formulation of Bayesian Statistics §

Hirophysics. com How this Relates to Court § A determination of guilt § Can determine, from a juror’s prior probability of a person’s guilt and evidence probabilities, how guilty a person could be § Turns preponderance of evidence and beyond a reasonable doubt to a mathematical problem instead of a personal guess § R v Adams 1996: § § § Victim did not identify Adams, 20 year age gap Had an alibi that was uncontested DNA match was 1 in 20 million Was convicted then appealed

Hirophysics. com Bayesian Method in R v Adams § Production of Bayes factors § It was him, but she could not identify him § It was not him, but she could not identify him § Remains convicted § Problem § Still relies on person probability statements § No way of determining evidential Bayes factors… yet

Hirophysics. com The Research Idea § To produce a program capable to accurately calculate a person’s probability of guilt based on evidential Bayes factors § To graph the progression of the probability of guilt for a visual reference § To make a practical program that could be tested in real trials

Hirophysics. com First Run Evidence Order: 1) 1. 0 2) 0. 8 3) 0. 6 4) 0. 4 5) 0. 2

Hirophysics. com Second Run Evidence Order: 1) 0. 2 2) 0. 4 3) 0. 6 4) 0. 8 5) 1. 0

Hirophysics. com Third Run Evidence Order: 1) 0. 6 2) 0. 4 3) 1. 0 4) 0. 2 5) 0. 8

Hirophysics. com Zero Prior Evidence Order: 1) 0. 99 2) 0. 8 3) 0. 6 4) 0. 4 5) 0. 2

Hirophysics. com Interesting Outcomes § Order of evidence input can alter the guilt probability § A prior probability of 0% will remain 0% no matter what the evidence shows § Prevents admissibility in court

Hirophysics. com Conclusion § The basic algorithm seems to have some challenges regarding evidence order and zero prior probability. It may need new parameters or the equation needs to be reworked. § Legal research needs to be conducted to give better percentage values to different pieces of evidence. As it stands now all values are based on personal opinion.

Hirophysics. com References § [1998] 1 Cr App R 377, [1997] EWCA Crim 2474 <http: //www. bailii. org/ew/cases/EWCA/Crim/1997/2474. html> § "Bayesian Inference. " Wikipedia. Web. <http: //en. wikipedia. org/wiki/Bayesian_inference#In_the_courtro om> § Bayesian statistics for dummies. (2005, February 1). Retrieved from <http: //web. vu. union. edu/~coulombj/Articles/SCIENCETECHNOLOGY/Bayesian%20 statistics%20 for%20 dummies/inde x. html> § Jordi. (2001, August 22). Bayesian statistics? [Online Forum Comment]. Retrieved from <http: //mathforum. org/library/drmath/view/52221. html>