'American Idol' Alum Caleb Flynn's First Prison Mugshot After Murder Conviction

Former "American Idol" contestant Caleb Flynn is settling in to his new digs in a state prison after being convicted of murdering his wife ... and we have the first look at his first mugshot.

Caleb is wearing a white shirt and an blue prison jumpsuit in the photo ... with a stone cold look on his face as he poses in front of a yellow background.

As you know, Caleb was sentenced to life in prison without the possibility of parole after being found guilty of murdering his wife, Ashley Flynn.

Caleb shot Ashley twice in the back of the head and staged the scene to look like a break-in ... he was having an affair and told his mistress the night before the murder, "I choose you. I'm free. Actions will come tomorrow."

Caleb's daughters ripped into him in letters read at his sentencing -- with his older daughter Alyssa saying she won't be visiting him in prison.