Mine have occasionally brought one in - alive! Polly caught them (too old now, bless her) but hasn't had any teeth since I've had her, no idea what happened to them; so she tried to gum the mice to death! Samantha would nick them off her and finish the job. They would then toss the body around - I left them to it. They've never actually eaten one, unlike Max, my previous cat, who caught birds and ate them, feathers, beak, claws - EVERYTHING in a few munches.
The worse one was Bella, an ex feral, who would greet me in the morning with the carcasses of birds and feathers strewn around the lounge! She'd be so proud!
Well, if we will love these little carnivores........