Constructing the Nanites
Sometime before 2015, Doctor Van Criss was employed by Wayne Enterprises' weapons department. Through his research at Van Criss Laboratories, he was able to develop the Nano-Bomb (or nanite): a powerful explosive that was small enough to be injected into a victim. Once detonated, it would cause the victim's head to explode. Amanda Waller purchased the Nano-Bombs and used them to control Task Force X.
Interrogated by the Joker
The Joker learned of the Nano-Bombs existence from Griggs, who also informed him of Van Criss' location. Joker and his gang then assaulted Van Criss Laboratories, using a bomb to incapacitate the security guard. After massacring countless doctors and employees, the Joker found Van Criss in a containment zone and his lackeys demanded he open the door, which Van Criss refused. Jonny Frost startled the doctor by firing at the shatterproof glass before the Joker showed him a live feed of his wife being tortured by his gang. She begged Van Criss to obey the Joker, so Van Criss opened the lab door, allowing Joker and Jonny Frost to enter. To force Van Criss to obey him, Joker injected him with a spare Nano-Bomb.
Joker brought Van Criss along with him during his rescue of Harley Quinn, as he was the only person who knew how to defuse the bomb. They were able to hijack one of Amanda Waller's planes, meeting her and Task Force X on the roof of a building. As Frost and Joker opened fire on Task Force X, Van Criss defused Harley's nano-bomb, allowing her to jump on board the plane. As they flew away, however, the plane was shot down by the United States Army on orders of Amanda Waller, causing it to crash. Though Joker survived, Van Criss perished in the explosion.