A Justice Department probe of an aggressive drug squad within the Philadelphia Police Department will likely hinge on the testimony this week from a corrupt officer-turned-informant.
Jeffrey Walker says he lied, stole and beat drug dealers during his years with the undercover Narcotics Field Unit.
The 46-year-old Walker has been in prison since he was caught planting evidence and stealing cash in a 2013 FBI sting.
He now admits committing "thousands" of crimes on duty.
He says countless drug suspects went to prison based on lies his squad made up to get search warrants, make arrests and win convictions.
Lawyers for six former colleagues now on trial call Walker a drunk, disreputable police officer and unreliable witness.
Walker is set to spend his third day on the witness stand Thursday.
