Law & Order, Season 3

[Cerreta and Logan are investigating the death of a teenager due to a defective pacemaker. They have discovered it was second hand, and was in somebody else beforehand.]

Cerreta:
This pacemaker has a lifespan of 5 years; That first cardiologist said it was in Mrs. Barnett for 3 years.

Logan:
That's right. And Halin said when he implanted it in Roberto, it was 3 years before the expiration date.

Cerreta:
How's your arithmetic?

Logan:
I know that 3+3 equals murder-2.