SANFORD, Florida (Reuters) - Lawyers for George Zimmerman asked a judge on Friday to consider acquitting the former neighborhood watch volunteer of second-degree murder charges in the killing of unarmed black teenager Trayvon Martin, arguing the state failed to meet its burden of proof.

The motion came as prosecutors prepared to rest their case in Seminole County court after nine days of witness testimony aimed at undermining Zimmerman's claim that he shot and killed Martin in self-defense.

Mark O'Mara, Zimmerman's lead lawyer, said there was "a very well-founded reasonable hypothesis of innocence" and that Zimmerman should be cleared of the charges.

(Reporting by Tom Brown and Kevin Gray)