> unrelated people recounted confessions he made to them that included details that were never made public

Do you have a source?

"The case against Mr. Williams turned on the testimony of two unreliable witnesses who were incentivized by promises of leniency in their own pending criminal cases and reward money. The investigation had gone cold until a jail inmate named Henry Cole, a man with a lengthy record, claimed that Mr. Williams confessed to him that he committed the murder while they were both locked up in jail. Cole directed police to Laura Asaro, a woman who had briefly dated Mr. Williams and had an extensive record of her own.

Both of these individuals were known fabricators; neither revealed any information that was not either included in media accounts about the case or already known to the police. "