Murder by Testimony - Digger Collins Mysteries, #3

Digger drives by the car accident scene of a friend. He knows in his heart that this was no accident. So, when he couldn't let the scene go, he asked FBI Agent Watson for help. Once they joined forces, Watson found a series of murdered scientists who died in a similar manner to Digger's friend. This spurred Digger to find the truth. While searching for the reason for the killings, Digger finds a file, and everything makes sense until a photo falls free.
Who is the girl in the photo?The deeper they dig into the deaths, the more they become a target. With Watson lying close to death in a hospital room, Digger must finish this case. Can he find the answers he needs to satisfy his burning question: Why would one's testimony lead to murder?