Law enforcement agencies and prosecutors from Colorado to New York have turned to a little-known artificial intelligence tool in recent years to help investigate, charge and convict suspects accused of murder and other serious crimes.

But as the software, called Cybercheck, has spread, defense lawyers have questioned its accuracy and reliability. Its methodology is opaque, they’ve said, and it hasn’t been independently vetted. 

The company behind the software has said the technology relies on machine learning to scour vast swaths of the web and gather “open source intelligence” — social media profiles, email addresses and other publicly available information — to help identify potential suspects’ physical locations and…