Please don't list this on a work's page as a trope. Examples can go on the work's YMMV tab.
Tear Jerker: Motive
"Framed": Pretty much the last quarter of the episode when you realize the motive for the murder.
"Deception": Stan, an old medical examiner, is dead and Betty, one of the other M Es, knew him well. She has to do the initial evaluation of the wounds which led to his death.
"Dead End": A girl, Janine, who has obsessive tendencies about her best friend, finds out her father had sex with said bff. In a fit of rage she kills her friend, and discovering the resulting pregnancy from that affair plus Janine's arrest for murder leaves her mother and her brother Aiden having to deal with a completely wrecked family.
"A Bullet for Joey": Three brothers are trying to keep a family business afloat and send their sister to dental hygienist school. When she discovers their financial problems and leaseback arrangement with a loan shark, she prostitutes herself to the loan shark, hoping to get a better interest rate in exchange. He reneges on the deal, which makes her break down crying, and which provokes her brothers to kill him.
"For You I Die": Angie has finally had to confront the reality and consequences of a ten-year cover-up, and she appears to be wondering if she can handle being a cop anymore.