A UC San Diego physics graduate student pleaded not guilty by reason of insanity Tuesday to attempted murder of a peace officer stemming from an incident last month when a CHP officer was shot during a struggle over his gun along a busy freeway in Mission Valley.

Yuhao Du, 25, also entered a standard not guilty plea during his brief arraignment in San Diego Superior Court, with his mother — Xiuqin Li, a physician who flew in from China to attend — in the courtroom.

After the hearing, Li read a statement, translated by her son's defense attorney Anna Demidchik.

"Yuhao has always been a very good, responsible, hardworking kid with big dreams. That's why we supported his desire to study physics in the United States. It breaks my heart to see him in this situation," Li said.

"But I trust the American justice system to get to the bottom of the problem and to come to the right resolution of this issue."

Du, who is in the United States on a student visa, could face life in prison if convicted.

Officer Tony Pacheco is recovering from a gunshot to his right thigh.

It is not common for a defendant to plead guilty by reason of insanity in San Diego, and it is rarely done at the initial arraignment when the case is still in its infancy.

Since 2010, the District Attorney's Office has filed more than 450,000 cases, data from the office show. Defendants pleaded not guilty by reason of insanity in just 87 of those cases. Among those cases, 13 people were found not guilty by reason of insanity.

No new details of the freeway incident were shared during Du's brief arraignment, which had twice been delayed since his arrest after the April 17 incident in evening rush hour traffic.

Authorities say Pacheco stopped to helped Du, who had crashed his car into a center divide along Interstate 8 under an Interstate 805 overpass during evening rush hour traffic. As soon as Pacheco arrived, they said, Du lunged at him.

People in the slowed traffic saw the struggle, and some rushed to help the wounded officer and restrain Du. The aftermath of the incident was captured in several cellphone videos.

It's not clear if the struggle or shooting was caught on camera. CHP officers don't generally wear body cameras, and authorities have not said the incident was recorded on his dashboard camera.

Demidchek said Du came to the U.S. in 2015 and graduated with two undergraduate degrees — one in physics and one in math.

She said Du's family is "shocked and heartbroken" by the situation.

In her statement after the hearing, Du's mother also offered sympathies from herself and her husband to Pacheco and his family, and wishes for a fast recovery.

"What happened must be extremely traumatizing not just for the officer to get hurt in the line of duty, but also to his family," Li said. "It must be heartbreaking for the officer's wife, who is carrying his child to go through this, and also to take care of their children."

Aside from attempted murder of a peace officer, Du is charged with assault on a peace officer with a semi-automatic firearm and attempting to take a firearm from a peace officer.

The criminal complaint includes several allegations, including intentional and personal use of the gun.

Superior Court Judge Laura Halgren ordered Du to remain jailed without bail. He is due back in court in July.

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