LOS ANGELES, Jul. 5 – Former Charles Manson follower Leslie Van Houten was convicted of first-degree murder today in her third trial for the Aug. 10, 1969, slayings of Leno and Rosemary LaBianca.

She also was found guilty of conspiracy to commit murder in the killing of five persons the previous night at the estate of actress Sharon Tate.

A six-woman, six-man jury reached the verdict after deliberating 34 hours over nine days following a four-month-long trial.

The jurors informed Superior Court Judge Gordon Ringer they had a verdict shortly after they arrived at the Criminal Courts Building this morning. But the announcement of the decision was delayed for more than three hours because Miss Van Houten’s attorney was en route from his Paso Robles ranch.

When the verdicts were read, the 28-year-old former homecoming princess at Monrovia High School stared straight ahead and tightly gripped the arms of the chair in which she was sitting.

The jury’s decision means that Miss Van Houten probably has several more years to serve in prison.

She already has spent eight years behind bars, having been released only six months ago pending the outcome of this trial when friends and members of her family were able to post $50,000 bond.

This third trial focused largely on the definitions of first-degree murder and manslaughter.

In his closing argument, Maxwell Keith, Miss Van Houten’s attorney, did not even ask the jurors to acquit her, but told them if they followed the law on diminished capacity the only proper verdict would be to find her guilty of manslaughter.

Voluntary manslaughter, the verdict asked for by Keith, is an unlawful killing without malice aforethought.

The defense contention was that Miss Van Houten suffered from diminished mental capacity due to Manson’s domination and her prolonged use of LSD, and Keith argued that, as a result, she could not “meaningfully and maturely premeditate murder.”

However, the jurors obviously disagreed and accepted the argument of coprosecutors Stephen Kay and Dino Fulgoni that her involvement in the LaBianca slayings constituted first-degree murder and that any other verdict would have been a “travesty of justice.”

Miss Van Houten had been convicted of first-degree murder at the conclusion of her first trial, in 1971, when she was tried jointly with Susan Atkins, Patricia Krenwinkel and Manson. None of the defendants presented any defense in that trial.

The convictions of the other three were upheld, but the state Court of Appeal granted a new trial to Miss Van Houten as the result of her attorney’s having disappeared in the midst of that first trial.

In her second trial, the jury ended up hopelessly deadlocked 11 months ago with seven votes for first-degree murder and five for manslaughter after 25 days of deliberation.

By BILL FARR