That disorder, Cherlin said, evolved into post-traumatic stress syndrome.
He further testified that based on information he was provided, Mostrong — when the crash occurred — saw his mother's face, a flashback image to the time when as a child he found his mother's body after she "overdosed and died," Cherlin said.
Cherlin said Mostrong has a history of post-traumatic stress syndrome as a result of finding his mother's body.
Espinosa suggested to Cherlin that if Mostrong was suffering from a disorder moments after the crash it could have appeared as if he was under the influence.
Cherlin responded that a person in such a state would appear dazed.
Espinosa asked, "It would be kind of an unconscious state?"
Cherlin responded: "You can call it that."
With that statement, Espinosa ended his questioning of Cherlin and Deputy District Attorney Wayne Robinson started his cross-examination.
Robinson is asking the jury find Mostrong guilty of vehicular manslaughter, hit and run and driving under the influence in connection with the crash.
According to testimony, Mostrong was at a party in the Superstition Mountains when he and others went for a ride in Mostrong's van.
At the same time, Michelle was in the area with friends.
Michelle, 17, of Alpine had gone for a drive in a golf cart with friend Charlotte Lang. Another friend, Eric Welter, was with them on his motorcycle.
The golf cart came to a stop on Wheeler Road facing south on the northern side of the road. It had apparently run out of gas.
The cart was still in the road with Michelle and her friends in or near the cart as Mostrong was driving his van on Wheeler. Shortly before midnight, the van hit Michelle, throwing her about 107 feet. She died at the scene.
According to testimony, Mostrong stopped the van down the road from the crash, his passengers got out and a friend, Kristoffer Purdy, got into the driver's seat and drove with Mostrong away from the scene.
When the van got a flat tire, the two walked to Imperial.
It was 17 hours after the crash when Mostrong turned himself over to the California Highway Patrol. It was then that his blood was tested and he was arrested.
The prosecution has argued the golf cart lights were on and Mostrong could not react because he was under the influence of alcohol and marijuana.
The defense has argued the cart's lights were not on and there was no way Mostrong could have seen the cart in time to react.
Espinosa also has said Mostrong was not under the influence. He added Michelle and Welter both had been drinking that night and neither was paying attention to the road or they would have seen the van coming.
On the issue of Mostrong's mental state on Oct. 7 and in the following months, Robinson focused on the fact Mostrong did not seek medical help until eight months after the crash.
Robinson also asked Cherlin if he had taken the time to look up any records on past counseling Mostrong had received after he found his mother's body.
Cherlin said he did not, adding he was attempting to treat his current condition.
"Didn't he relate his mother's death was a flashback?" Robinson asked.
"Yes, he did," Cherlin said.
"But you never looked at past records?" Robinson asked.
"No, I didn't," Cherlin answered.
Robinson, in looking over the records of Mostrong's visits with Cherlin, showed Cherlin a section of a medical questionnaire Mostrong had filled out in which he was asked to describe the problem that brought him to the doctor.
Robinson asked Cherlin to read what Mostrong had written as a response.
Cherlin responded Mostrong wrote that his attorney had sent him to the doctor.
Robinson also asked Cherlin if Mostrong admitted to the doctor that he drinks alcohol and smokes marijuana.
Cherlin responded Mostrong did admit to both drinking and smoking marijuana, but Mostrong told him he had not been drinking or smoking marijuana on the night of the crash.
On Friday, the Mostrong trial will continue with Robinson calling to the stand "rebuttal" witnesses.
Next week, both attorneys could give their closing arguments and the case, after a month of testimony, could go to the jury.
Espinosa has already indicated if the jury rules against Mostrong he would follow through with the appeals process based on a ruling by Contreras earlier in the trial that prevented Espinosa from calling to the stand a witness who was to testify regarding injuries Welter had on his genitals.
Contreras declined to allow such testimony, stating it could be prejudicial to the jury.
Staff Writer Darren Simon can be reached at 337-4082.