Porn queen Jenna Jameson had a bit of a setback en route to her birthday celebration on Sunday, April 7, when she was arrested for allegedly battering her assistant after an argument. But we bet you can't guess what her weapon of choice was.

Not only did Jen deliver a helluva smackdown -- but she did it with a brass knuckle iPhone case like a tech-savvy, amply-bosomed mobster.

Jenna's transgendered assistant Britney Markham, who also happens to be a porn star (we know, it's all very confusing), has filed a restraining order against Jameson, and TMZ reports those documents reveal new details of the assault.

Supposedly, Jameson burst into a Newport Beach, Calif. salon and started an altercation before striking Markham in the stomach and back with the lethal phone and yelling "I'll f--king kill you!"

Markham ended up in the hospital, and Jenna ended up in booking. But can Siri be charged as an accomplice?

For the record, brass knuckles are illegal in California, but Jenna is claiming they're an accessory, not a weapon. Which makes sense, until you beat someone up with them.

Here's photographic evidence of the deadly device:

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