The California Supreme Court Thursday unanimously upheld the death penalty of a Berkeley man who fatally shot his sister and her son after a series of arguments.

Erven Blacksher, now 46, was convicted in Alameda County Superior Court in 1998 of the first-degree murder of his nephew, Torey Lee, 21, and the second-degree murder of his sister, Versenia Lee, 46, on May 11, 1995.

He was sentenced to death the following year on the basis of a jury finding of a special circumstance of multiple murders.

The victims were living at the home of Blacksher's and Lee's mother, Eva Blacksher, in West Berkeley.

Erven Blacksher, the youngest of eight siblings, had moved to a back cottage on the property to enable his sister to live in the house while taking care of their mother.

According to testimony at the trial, the early-morning shootings came after several days of arguments between Blacksher and his nephew.

Other family members testified Blacksher told them he planned to get a gun and kill his nephew because of the young man's alleged cocaine dealing and disrespect toward him and Eva Blacksher.

Blacksher, who had previously been hospitalized several times for episodes of mental illness, argued at the guilt phase of his trial that he lacked the ability to form an intent to murder because he suffered from paranoid schizophrenia.

He also argued in a separate sanity phase of trial that he was insane at the time of the shootings.

But the jury rejected both those arguments.

In Thursday's decision, issued in San Francisco and written by Justice Carol Corrigan, the state high court rejected a series of appeal claims in which Blacksher challenged evidence rulings and jury instructions at his trial.

Blacksher can continue appeals through habeas corpus petitions in the state and federal court systems.