Monday, 11 September 2017

An objective prior probability for guilt?



One of the greatest impediments to the use of probabilistic reasoning in legal arguments is the difficulty in agreeing on an appropriate prior probability that the defendant is guilty. The 'innocent until proven guilty' assumption technically means a prior probability of 0 - a figure that (by Bayesian reasoning) can never be overturned no matter how much evidence follows. Some have suggested the logical equivalent of 1/N where N is the number of people in the world. But this probability is clearly too low as N includes too many who could not physically have committed the crime. On the other hand the often suggested prior 0.5 is too high as it stacks the odds too much against the defendant.

Therefore, even strong supporters of a Bayesian approach seem to think they can and must ignore the need to consider a  prior probability of guilt (indeed it is this thinking that explains the prominence of the 'likelihood ratio' approach discussed so often on this blog).

New work - presented at the 2017 International Conference on Artificial Intelligence and the Law (ICAIL 2017) - shows that, in a large class of cases, it is possible to arrive at a realistic prior that is also as consistent as possible with the legal notion of ‘innocent until proven guilty’. The approach is based first on identifying the 'smallest' time and location from the actual crime scene within which the defendant was definitely present and then estimating the number of people - other than the suspect - who were also within this time/area. If there were n people in total, then before any other evidence is considered each person, including the suspect, has an equal prior probability 1/n of having carried out the crime.

The method applies to cases where we assume a crime has definitely taken place and that it was committed by one person against one other person (e.g. murder, assault, robbery). The work considers both the practical and legal implications of the approach and demonstrates how the prior probability is naturally incorporated into a generic Bayesian network model that allows us to integrate other evidence about the case.

Full details:
Fenton, N. E., Lagnado, D. A., Dahlman, C., & Neil, M. (2017). "The Opportunity Prior: A Simple and Practical Solution to the Prior Probability Problem for Legal Cases". In International Conference on Artificial Intelligence and the Law (ICAIL 2017). Published by ACM. Pre-publication draft.
See also

5 comments:

  1. Am writing this great article to appreciate the good work of Doctor Omoluyi. I have been married for 2 years with pain and agony because my husband left me for another lady. I was reviewing some post on the internet on how i could get back my husband then, i saw a post by Lori Dante from Germany who testified of Doctor Omoluyi the almighty spiritual caster. I contacted Lori Dante to confirm about Doctor Omoluyi and she guaranteed me and gave me the courage to contact Doctor Omoluyi for help. So, i contacted him and he assured me that my days of sorrows are over that i will get back my husband within 12 to 16 hours. I did all what he told me and am very happy today that my husband is back to me and we are now living happily like never before and i can boldly and proudly testify to the world that Doctor Omoluyi is a good and remarkable helper that specializes on different kind of spells. If you need his help, then contact him on E-mail: ( doctoromoluyispelltemple@gmail.com ) OR Text +1 (914)-517-3229 for more info.

    ReplyDelete
  2. Its very imppressive article for us thankkk you.
    Safety and risk management is a vital part of any Australian business. However doing it right and in line with the new Australian WHS legislation is a complex task where many variables need to be considered.

    ReplyDelete
  3. How To Get Back With Your Ex, Get A Fast Love Spell, A Real Spell Caster To Be Trusted And To Help You Is Dr happy The Man God Has Sent To Help Us Hi, my bf broke up last week , and I regret it cuz I’ve wasted all his love , we work on a same company together , and he’s ignoring me , I didn’t do anything after out break up , damn I hate my pride , and now I regret all the days I’ve wasted , I’m still texting him everyday , like once/day , like goodmorning.. take care.. or did u take ur lunch , later on I receive a message from him saying that please stop texting me , don’t pretend u care cuz I really don’t care, get ur own life , and I said I’m not pretending and this is how I really feel and I said I’m sorry , and he says stop it , it’s over ,what else should i do i really love this guy and i want to get back with him i have try every thing i could but it did not work out am heart broken and stress out coz this guy mean a lot to me. i pray and cry all day that he will fine a place in his heart to forgive me and come back to me. so i decided to look for help to see if i can get my bf back i try all means to the stage of applying for a love spell from different spell casters but no one could work out after sending money to them they keep telling me different stories, i was totally down about to give up coz i have spend so many money on him trying to see if i can get him back so i read and come across a site http://happylovespell2.webs.com/ with a wonderful testimony of a real spell caster call Dr happy i never believe coz i have try so many spell casters i said to my self let me give to the last try i email Dr happy urgently on happylovespell2@gmail.com explain my problem to him do what he ask of me even when i have to borrow up some money he ask i did and he give me reassurance that with 27 hours after the spell, my bf who left will come back for me , i still never believe i was doubting his judgement not knowing that he is the real man who god has sent to restored and bring back my bf. so as he promise, after the spell my bf reply back to my test messages, call me, and apology to me so the following day my bf come back home to me and since them we are living happily plz i will advise any one to contact Dr happy for a love spell to get ex back and save broken marriage, restored relationship problem so email him now at happylovespell2@gmail.com also call and add him up on whats-app +2348133873774

    ReplyDelete
  4. At last my happiness and joy has been restored as my husband who left me for another girl has finally come back good and still lovely to me , i want to use this time to give thanks to Dr Blessing who has use his love spell and prayers to bring back my ex lover and also share little about my rough story between me and my husband and the other girls , i got married to the man i loved Sanchez June 23 2013 and we have been together ever since and we have leaved happily we both have a daughter , but this year 2017 when has traveled to new York on a business things changed even when he was away he never called to say hi to me and my daughter and this was unlikely of him because he loves our daughter to sky , so i began to suspect something wasn't right, but i waited for he to return to me in Canada so i know what the problems was, only for Sanchez to come back asking for divorce at first i thought he was joking , but with time i saw he was so serious on this , i tried to plead with he but nothing changed , i called my mom telling her about the situation and she said to pray about it , i was depressed and devastated on this issues and was praying and looking for help to stop the divorce and save my marriage, i seek help with many persons non could help , i continue with the search of help because i knew and have the feelings my man was not on his right senses because i know the man i married can never ask me for a divorce, so i kept on looking for solutions i spent almost all my savings seeking solution , until the Juliana a working told me about Dr blessing of blessingspiritualtemple@gmail.com, i never wanted to email him because many has taken money from me without giving any good result, but when he gave her words about Dr Blessing i decided to give it a trial , contacted him and told him about myself , he told me that he will have me to make my husband stop the divorce and reunite us again , that he gave me three days after which everything will be back to it normal place for good , i did some few things he said i should do as instructed , and let he do his work i was at work on the 15th of July about 10 AM when i received letter from my husband that my husband has cancelled the divorce case and same day at about 12 noon my husband wrote me a sweet text , and this was how me and my husband came back and today we are better as one family , so i want to use this means to tell to you all here contact Dr Blessing to for any kind of relationship or married problems and i let he solve it for you just as he has done for me , his contacts
    Email; blessingspiritualtemple@gmail.com
    Whats,App. +1(951) 409 0694

    ReplyDelete
  5. Advice for heart broken and how to get your Ex lover back and he will apologize for his mistake and the pain he caused you!..I highly recommends this real spell caster Dr.Unity to anyone in need of help! I am so excited i got my husband back after he left me for another woman. After 12 years of marriage, me and my husband has been into one quarrel or the other until he finally left me and moved to California to be with another woman. I felt my life was over and my kids thought they would never see their father again. i tried to be strong just for the kids but i could not control the pains that torments my heart, my heart was filled with sorrows and pains because i was really in love with my husband. Every day and night i think of him and always wish he would come back to me, I was really upset and i needed help, so i searched for help online and I came across a website that suggested that Dr Unity can help get ex back fast. So, I felt I should give him a try. I contacted him and he told me what to do and i did it then he did a (Love spell) for me. 28 hours later, my husband really called me and told me that he miss me and the kids so much, So Amazing!! So that was how he came back that same day,with lots of love and joy,and he apologized for his mistake,and for the pain he caused me and the kids. Then from that day,our Marriage was now stronger than how it were before, All thanks to Dr Unity. he is so powerful and i decided to share my story on the internet that Dr.Unity real and powerful spell caster who i will always pray to live long to help his children in the time of trouble, if you are here and you need your Ex back or your husband moved to another woman, do not cry anymore, contact this powerful spell caster now. Here’s his contact:
    Email him at: Unityspelltemple@gmail.com ,
    you can also call him or add him on Whats-app: +2348071622464 ,
    you can also visit his website:https://unitysspelltemple.blogspot.com .

    ReplyDelete