Michelle died after she was thrown an estimated 107 feet.
Mostrong stopped his van a distance from the crash site and his friends got out and ran from the scene. One friend, Kristoffer Purdy, put a shocked Mostrong in the passenger seat and then drove him away from the scene.
At some point the van suffered a punctured tire and Mostrong and Purdy walked to Imperial, stopping at Imperial High School, where they called for a ride.
Nearly 17 hours later Mostrong turned himself in to the California Highway Patrol at its Imperial headquarters.
Those are the facts of the case not in dispute.
In their closing arguments Monday, Robinson and Espinosa painted different pictures of what occurred in the moments leading to the crash and about who was to blame.
Robinson is asking the jury to find Mostrong guilty of vehicular manslaughter, driving under the influence and hit and run.
He told the jury that testimony he had presented showed witnesses had seen Mostrong drinking and passing around a marijuana joint.
Robinson, who has contended the lights on the golf cart were on and as such the cart was visible, asked a rhetorical question as to how someone would not have seen lights ahead on Wheeler.
"He was so under the influence he didn't know," Robinson said. "A divided attention or a lack thereof. You can't do two things at once."
Robinson argued that authorities do not know what Mostrong's blood-alcohol level was because he left the scene of the collision.
"It's no one's fault but the defendant's," Robinson argued. "He left the scene. You would think if a person was innocent they would stay."
Robinson attempted to counter a defense argument that Mostrong was in a semi-conscious state after the accident because of posttraumatic stress syndrome.
Robinson said undoubtedly those in the van when the collision occurred were in shock because a girl's face had just struck the windshield.
"This young man has not learned he had to be responsible for his actions," Robinson argued, adding when an individual takes another's life the person has to take responsibility for that action.
Espinosa argued Mostrong was not to blame for the accident and that the blame actually lies with Michelle and those she was with.
Espinosa has contended throughout the trial the golf cart, which Michelle and friend Charlotte Lang had been driving on Wheeler on Oct. 7, stopped in the northbound side of Wheeler in the line of traffic.
He has argued the cart did not have its lights on and those with the golf cart should have moved it off the road.
On Monday Espinosa told the jury that even after the testimony he provided through an accident reconstructionist, Robinson is still contending the lights of the golf cart were on.
Espinosa attacked the testimony of Blake Reed, who was in the van at the time of the accident and testified he saw lights ahead and told Mostrong to slow down.
"Blake Reed was the star," Espinosa said. "Young Blake is as big a liar as I have ever seen come forward and not be prosecuted by somebody."
Espinosa said Reed testified he thought Mostrong was intoxicated before the crash, but in earlier taped interviews he said he did "not have a clue" in regard to Mostrong's sobriety.
Espinosa said it was fortunate that Christina Ruiz, who was at the party on Oct. 7, testified that Reed himself was so under the influence he threw up at the party.
"That liar never told us that," Espinosa told the jury.
Espinosa asked the jury members how many of them driving down a road would expect a vehicle to be in their path with the lights off.
"It is truly sad when anyone suffers a loss of life in an accident," Espinosa said, adding, "An accident is just that; it's an accident."
Espinosa said blame for Michelle's death also rests with her parents, who allowed her to go with a 37-year-old man and a 19-year-old man to the desert.
In summary, Espinosa said, "Blake Mostrong was in the wrong place at the wrong time."
Following the closing arguments, the jury was given instructions by Superior Court Judge Matias Contreras and the case was handed over for deliberations.
The jury was expected to continue deliberations at 9 a.m.
Staff Writer Darren Simon can be reached at 337-4082.