Jared Cardon resigned after being charged and hopes to rejoin law enforcement now that his name has been cleared.
Cardon says the fleeing motorist threatened him and others backed up at a traffic stop with erratic driving.
Some witnesses insisted the motorist was trying to drive around the police officer, not at him. But Cardon's attorney, Linsday Jarvis, says other witnesses backed the officer's version of events.
Salt Lake County District Attorney Sim Gill says he dropped the charge because of changing expert testimony in the case. He wouldn't elaborate.
About 20 fellow officers accompanied Cardon to 3rd District Court on Friday when the charge was dropped.
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