He turns and gives a signal nod to another inmate. The inmate moves towards a C.O. overseeing the line-up and punches him in the face.

Researchers believe this chemical signal may also play a role in how other body parts, like the kidneys, eyes, ears, nose, and face, develop.

He pulls a black hood over Lincoln's face and gives the signal to two C.O.S who pull the control switch.