dr. david posey. coroner, who after two years changed his opinion from undetermined to homicide. posey tells jurors dee dee's body spoke loud and clear. that those bruises are signs that bohana severely beat dee dee before she drowned in the pool. for the prosecution, who was the key witness? >> dr. posey. >> reporter: clearly he was. >> without a doubt. >> reporter: but don't forget, the defense has its own star forensic pathologist on standby, dr. michael baden. >> i expected to go out there. i was told i was going to go out and testify. >> reporter: but as the trial progresses, bohana and his family, including ex-wife sheila, whom he's still close to, are mystified. where is dr. baden? >> why isn't he calling dr. baden? everybody else put on their people. >> reporter: you think dr. baden would have made a difference? >> oh, indeed. the world's greatest pathologist? my gosh. >> reporter: but harlan braun never calls dr. baden. in fact, braun doesn't call a single expert witness. and in a curious gam