Espinosa said Sperber was being called to testify that Eric Welter, the San Diego man struck along with Michelle on the night of Oct. 7 on Wheeler Road in western Imperial County, had injuries unrelated to being hit by a vehicle.
Welter, of the San Diego area, had been on Wheeler with Michelle and another girl, Charlotte Lang, on the night Mostrong's van crashed into the golf cart in which Michelle and Charlotte had been riding.
The golf cart had come to a stop on Wheeler. Welter, who was on his motorcycle, stopped alongside the cart.
When Mostrong's van hit the cart and Welter's motorcycle, Michelle was thrown about 107 feet. She died at the scene. Welter, also struck, survived and testified earlier in the trial.
Espinosa told Contreras Sperber was going to discuss that Welter had bite marks on his private areas.
Espinosa has said the lights of the golf cart were not on because of the activities of Welter and Michelle.
The issue over whether the golf cart's lights were on has been an ongoing debate. The prosecution had argued the lights were on. The defense has argued the lights were not on, making it impossible for Mostrong to have seen the cart.
Espinosa said of Sperber's testimony regarding the bite marks, "It will show they are the cause of their own fate."
Robinson said Sperber's testimony had no relevance. He said Espinosa was simply trying to discredit Michelle and to allow such testimony would be "highly prejudicial" to the jury.
Robinson argued that whatever was going on between Welter and Michelle had no bearing on Mostrong's actions that night.
Contreras, ruling the jury would not be allowed to hear Sperber's testimony, said he was concerned such testimony would be prejudicial.
Espinosa responded that Contreras was cutting into his ability to defend his client.
"Perhaps the court might as well shackle my client and take him to the gallows and hang him," Espinosa said.
He added the issue of the bite marks would allow him to follow through with his theory that Michelle and those she was with were not paying attention to what was going on around them.
While Contreras did not allow the testimony Friday, he did say the defense could continue to try to show why such testimony should be heard.
The second strike against the defense's case came later Friday as Espinosa called Edward Sherlin, a clinical psychologist who works in both San Diego and Imperial counties.
Sherlin testified that on June 6 he evaluated Mostrong and he has seen Mostrong as a patient four times since then.
Robinson objected to the testimony Sherlin was expected to give and the jury was removed from the courtroom.
Robinson said Mostrong saw Sherlin eight months after the Oct. 7 crash, adding he could not see the relevance to the case.
Espinosa told Contreras Sherlin was going to testify that Mostrong suffers from posttraumatic stress syndrome related to his finding the body of his mother in their home when he was a child after his mother killed herself.
Robinson argued at best that was a mitigating factor that could become an issue during a sentencing phase.
"It has nothing to do with a legal defense," Robinson argued.
Espinosa contended on the night of the accident, the moment Mostrong's van was involved in the accident, the posttraumatic stress syndrome he suffers from recurred.
Espinosa said Mostrong had little idea what was happening after the crash and his client had amnesia from the time the crash occurred.
"Immediately his mother's face flashed before him and he had no recollection," Espinosa said. "He just knew someone was driving him out of there."
Contreras ruled he would allow Sherlin to testify before the jury but he delayed the testimony, stating Espinosa has to make Sherlin's notes about Mostrong available to the prosecutors to review.
Contreras added after the prosecutors reviews the notes, he still may decide not to allow the testimony.
Contreras' stated one concern is Mostrong has not entered a plea of insanity, adding he is not sure Sherlin's testimony can serve as a defense.
Staff Writer Darren Simon can be reached at 337-4082.