Was Karen Read's Boyfriend John O'Keefe Really Killed by a Dog?

A key witness for Karen Read's defense, Dr. Marie Russell, took the stand to say that Read's boyfriend, ex-Boston Cop John O'Keefe, was killed by a dog. Read's defense team claims O'Keefe was beaten inside a house during a party, then dragged outside where a dog attacked him. During cross-examination, prosecutors wondered if Russell had memory issues. One of the first defense witnesses called by Read was ex-cop Kelly Dever, who, the defense says, changed her story on the stand, which she denies.