A Matter of Principle begins with a young woman being raped and murdered in her apartment by a masked assailant. Nearby, Bob Denvo (Robert Lyons), a man with a prior charge for assaulting a female, is seen acting suspiciously and apprehended by police as a suspect. At the coroner lab, a pathologist matches bite marks on the victim to cast molds of Denvo's teeth, but Sam (Robert Ito) runs his own newly developed test using a specialized microscope which disputes the original findings indicating the attacker was not Denvo. Lt. Monahan (Garry Walberg) and the District Attorney (John O'Connell) blast Sam for casting reasonable doubt on their case against Denvo which is going to trial, but Sam is convinced that his test is correct which means that the killer is still out there.
This is a fairly good episode which has Sam taking the lead in the story with Quincy (Jack Klugman) playing more of a supporting role. We saw something similar in the previous episode, but unlike that one at least it was one of the series regulars that was promoted to lead for a week here rather than an unfamiliar guest star. I think the substitution is more acceptable under this scenario. There is a crime as well as a decent murder mystery featured which keeps things interesting. I have to say that I also particularly enjoyed the scenes where the usually mild-mannered Sam gets fed up with Monahan's rude and dismissive attitude towards his findings and finally stands up to him. You tell him Fujiyama!!
Overall, this is a worthwhile second episode of Season 6 which is a huge improvement over the previous one and should be of particular interest to the Sam/Robert Ito fans as he takes on a more substantial role in the story.