but where was david dooley? because he was the janitor, he didn't use a scanner. aid the prosecutor, he could have been upstairs near michelle's office during that critical time. the jury got to see dooley on security video from that morning. >> there's the red pick up truck. >> reporter: his red truck was seen leaving the thermo fisher parking lot. >> the defendant actually left the building that day at 6:31 am which was about a half an hour after michelle walked into the building. >> reporter: the prosecutor showed the jury a photo of fresh pry marks on michelle's office door which she said indicated an attempted break-in. >> our belief has always been that david dooley was in the middle of breaking into her office when she came up the steps and surprised him. and ultimately she was assaulted and restrained. >> because she was a witness to a crime in progress. >> absolutely. >> reporter: the medical examiner said michelle was bludgeoned to death with something similar to an industrial packing tape gun. but after such a violent attack, why was no blood evidence ev