When did bulging eyes become a lethal weapon?

I listened to police officer Jason Van Dyke's live testimony with dismay in his trial for murder of Laquan McDonald. Just before shooting, Van Dyke offered this bizarre explanation:

“His [Laquan’s] face had no expression, his eyes were just bugging out of his head. He had these huge white eyes, just staring right through me.” Having remarked about McDonald's bulging white eyes several times before he shot him 16 times, it was clear Van Dyke was trying to invoke sympathy, even justification for his conduct.

Do you suppose instructors at the police academy warn all new recruits to beware the 'bulging white eyes'?