While there was little chance to argue on the motion for a new trial, Espinosa did state the jury's conviction was unlawful.
Deputy District Attorney Wayne Robinson stated there was nothing unlawful about the conviction.
A jury in July found Mostrong guilty of vehicular manslaughter in the Oct. 7 death of Michelle Marie Grady, 17. The jury also determined Mostrong was guilty of driving under the influence and hit and run.
Mostrong was driving his van from a party in western Imperial County in the Superstition Mountains when the van struck Michelle, throwing her 107 feet. She died at the scene.
Michelle had been riding in a golf cart with a friend on Wheeler Road when the cart came to a stop in the road.
Michelle was near the cart with two friends when Mostrong's van struck the cart, Michelle and one of her friends, Eric Welter.
Through nearly six weeks of testimony, the prosecution presented a case that Mostrong had been drinking and smoking marijuana while at a party and that his actions led to the fatal accident.
Espinosa argued Mostrong was not under the influence and that the accident resulted from the cart, Michelle and those she was with remaining in the road in the path of oncoming vehicles.
Mostrong left the scene and did not turn himself in until Oct. 8, several hours after the accident. His blood showed no signs of alcohol but he did have marijuana in his system.
However, it was stated in court that the marijuana he had in his system had been smoked only a short time before he turned himself in, not before the accident.
Espinosa has said he is prepared to appeal the conviction. That would not happen until after the sentencing. If the motion for a new trial is accepted, there will be no sentencing.
Staff Writer Darren Simon can be reached at 337-4082.