It is Roger Murtaugh's primary weapon in the Lethal Weapon Series and the second most used weapon overall, after Martin Riggs' Beretta 92. Whenever Murtaugh pulls out his gun, he rolls his neck clockwise before firing at his opponent.
Murtaugh first shows off his Model 19 revolver at the shooting range when on his 50th birthday, he shoots all his rounds on the target paper, then flicks the switch and whispers to himself "Happy Birthday Rog".
It is shown again when he is partnered with loose cannon Martin Riggs. Riggs quotes that Murtaugh's gun is "one of those old timers", seemingly offending Murtaugh.
After Riggs saves McCleary, Murtaugh gets upset at how he handled it and tests Riggs about his sanity by pointing the barrel of his Model 19 underneath his chin. Riggs moves it out of the way before he pulls the trigger.
Later at a house, Murtaugh guns down a suspect with his revolver and approaches him slowly for questioning.
Murtaugh uses his gun in combat against Shadow Company at El Mirage Lake as part of an attempted ambush in rescuing his daughter Rianne. At the club, Murtaugh takes out a couple mercenaries before he fires his lone revolver bullet at the driver of General Peter McAllister's getaway car.
Roger Murtaugh draws his weapon one last time, together with Martin Riggs as they simultaneously shoot Mr. Joshua in the chest, killing him.