Luigi Mangione Lawyer Wants State Murder Case Tossed After Federal Guilty Pleas

Luigi Mangione's lawyer says his federal guilty pleas should knock out the state murder case against him ... arguing he can't be prosecuted twice over the same killing.

Attorney Karen Friedman Agnifilo spoke outside the courthouse Friday after Mangione pleaded guilty to federal charges in the killing of UnitedHealthcare CEO Brian Thompson ... saying her client has now accepted "full responsibility" for Thompson's death.

Agnifilo says Mangione suffered years of severe pain from a broken back and believed the healthcare and insurance systems had failed him ... but her big argument Friday was that the killing was one event, and Mangione shouldn't be prosecuted twice for it.

In fact, his lawyers aren't wasting any time ... Agnifilo has filed a motion, obtained by TMZ, asking a judge to toss the state case under New York's double jeopardy protections.

Mangione's state trial is currently set to begin September 8.

U.S. Attorney Jamie McDonald had a much different message outside court ... calling Thompson's murder "deliberate, calculated, and premeditated" and stressing Mangione pleaded guilty without a plea agreement, meaning prosecutors gave him no concessions.