In this episode it is stated, that Quincy worked as a surgeon in the past, before becoming a coroner. But in the episode "A Star is Dead" from season 1, he says that he had a private practice in the past (or at least he says that he doesn't have it anymore). These two facts doesn't really seem to match, although it is possible that both are true.
Until this episode, we knew almost nothing about Quincy's past life or at least his life before the show started. In this episode we learn some maybe surprising facts about Quincy's past life. We learn that he was married once to a woman called Helen, that she wanted kids while he didn't want some, at least not "now". Later we learn, that Helen got a brain tumor and died of it, and that Quincy blames himself for the death of his wife, because he didn't have enough time for her and didn't see the symptoms of the fatal illness. People who see this episode maybe will see Quincy in a different light now. You could say that this is the first episode in the show, where Quincy is portrayed as a "normal" person with personal issues, and not (or at least, not through the whole episode, because he also solves a crime in it) as the kind of superhero, as which you could see him in most of the episodes of the show.
This episode marks the first appearance of Anita Gillette in the show, who plays Quincy's first wife, Helen, in some flashbacks during the episode. Ironically Gillette reappears in season 8, now as a main character, playing Quincy's girlfriend and later in the season his second wife, Dr. Emily Hanover. Ironically you could say that Quincy married the same person two times.
When Dorrie Larkin (played by actress Jane Greer) appears on the talk show near the end of the episode, the host introduces her with a clip of one of her movie appearances. However, the clip is actually of Jane Greer's 1959 guest appearance on the television series Bonanza.
2nd visit to garage Quincy has tie no sweater, he then arrives at sisters house with no tie and sweater.
Outside garage, Quincy is leaning on the detective with his medical gloves on. Next scene he moves away but gloves have gone!
As is mentioned in the episode itself, the method by which Dr. Astin and the Lieutentant use to match the bullet to the murder weapon has been dismissed as being scientifically unsound because the chemical composition of its particles can be matched directly to the other bullets in the same series and thus cause confusion as to which weapon is the murder gun.
I learned this from the TRUTH IN JUSTICE website.
Goof: As race car driver Mark Hellman readies for his qualifying round (after promising Quincy to tell him all he knows afterwards), a close up shows him wearing a pair of white socks and white KSwiss leather lace-up sneakers / trainers. After his crash, as he's put into the ambulance he's now wearing a pair of black shoes with red trim.