Poison (2001)

Detectives Ed Green and Lennie Briscoe from the 27th Precinct report a suspicious cyanide poisoning to the Major Case Squad. When other cyanide deaths occur in a hospital, Goren and Eames initially suspect Colleen Braxton, a nurse who fits the typical criminal profile, but the poisonings continue while Braxton is in custody. The source of the cyanide is tracked down to a batch of laced over-the-counter Necedrol pills. The investigation turns to the victims' families which leads the detectives to Trudy Pomeranski. The detectives discover she killed her husband and sued the medicine company, then laced other boxes of the same medication around the city in an attempt to cover-up the murder and strengthen her lawsuit.