Winfield will testify along with Pvt. Jeremy Morlock, who pled guilty to three murders and was sentenced to 24 years in prison last March. He has been cooperating with prosecutors since then. The credibility of Morlock's testimony has recently been called into question by investigators and defense attorneys, in light of 'inconsistent testimony' and the fact that Morlock recently requested court transcripts and investigative documents, saying they help him remember the relevant events. Since last year, Morlock said that it was Gibbs who would randomly choose civilians to kill and plan scenarios to make it look like they were killed in action.
More information about Winfield's plea deal and his role in the crimes can be accessed here.