The man in front of you has been caught in possession of drugs. He has no weapons, and no record of any violent or serious crimes. Do you let the man out on police bail the next morning, or keep him locked up for two days to ensure he comes to court on Monday?" The kind of scenario Dr Geoffrey Barnes is describing – whether to detain a suspect in police custody or release them on bail – occurs hundreds of thousands of times a year across the UK. The outcome of this decision could be major for the suspect, for public safety and for the police. "The police officers who make these custody decisions are highly experienced," explains Barnes. "But all their knowledge and policing skills can't tell them the one thing they need to now most about the suspect – how likely is it that he or she is going to cause major harm if they are released?

Police at the "front line" of difficult risk-based judgements are trialling an AI system trained by University of Cambridge criminologists to give guidance using the outcomes of five years of criminal histories. The man in front of you has been caught in possession of drugs. He has no weapons, and no record of any violent or serious crimes. Do you let the man out on police bail the next morning, or keep him locked up for two days to ensure he comes to court on Monday?" The kind of scenario Dr. Geoffrey Barnes is describing – whether to detain a suspect in police custody or release them on bail – occurs hundreds of thousands of times a year across the UK. The outcome of this decision could be major for the suspect, for public safety and for the police. "The police officers who make these custody decisions are highly experienced," explains Barnes. "But all their knowledge and policing skills can't tell them the one thing they need to now most about the suspect – how likely is it that he or she is going to cause major harm if they are released?

Hart has limitations currently based solely on offending data from Durham Constabulary and does not have access to information in the police national computer, said Ms Urwin. Which called as a problem Helen Ryan, head of law at the University of Winchester, also she added." Even without this system, [access to sufficient data is] a problem for the police." However she thinks the system is interesting in principle and that it had the potential to be hugely beneficial following extensive piloting. " I think it is actually a very positive development, " she added." I think, potentially, machines can be far more accurate –given the right data-than humans."

Police in Durham are preparing to go live with an artificial intelligence (AI) system designed to help officers decide whether or not a suspect should be kept in custody. The system classifies suspects at a low, medium or high risk of offending and has been trialled by the force. It has been trained on five years' of offending histories data. One expert said the tool could be useful, but the risk that it could skew decisions should be carefully assessed. Data for the Harm Assessment Risk Tool (Hart) was taken from Durham police records between 2008 and 2012.