Seen few on forensic files. One I remember was a tech stole propofol to treat his love interest's headaches and overdosed her. Charged with murder.
Few cases of jilted lovers, mostly nurses and vet techs injecting their victim with sux thinking its untraceable.
One med student overdosed his lover with lidocaine causing asystole during a breakup.
Worst offender I recall was an ahole former peds ICU nurse who had a habit of injecting kids with sux at a pediatricians office after she was canned from the hospital for suspected similar behavior. I guess was addicted to acting as the hero to save the day.