Criminologists say the system works - it can identify those most likely to commit violent crimes. But whether Philadelphia can use that to intervene and change people's behavior is still not known. A full evaluation won't be done until the end of the year.
Yet some probation officers say the changes already are making it far harder for them to help those at lower risk to get off drugs and improve their lives.
The controversy over the new system cuts to the heart of a long-standing debate: whether parole agencies should control dangerous people or help them reclaim their lives.
The computer isn't merely crunching data - it is creating its own rules in what is known as "machine learning," a fast-growing technology that enables computers to encroach into the human realms of judgment and decision-making.
The Adult Probation and Parole Department started considering a technological upgrade in 2006, the year the murder rate hit a peak of 27.8 per 100,000 inhabitants, the highest of any of the nation's 10 largest cities.
University of Pennsylvania criminologist Larry Sherman suggested the department go high-tech, with the help of University of California statistician Richard Berk.
At the time, Berk had been doing computer modeling for the California prison system. "We were forecasting what types of inmates are likely to do nasty things in prison," he said.
Later that year, Berk took a job at Penn and started applying his statistical skills to predicting murder. He later added assault and robbery. "The idea was to forecast who the real bad guys were - so you could deliver special services to them and reduce the number of homicides," he said.
