MARTINEZ, Calif. -- A 16-year-old youth has been arrested in connection with the fatal bludgeoning of Pamela Vitale, the wife of defense attorney and television analyst Daniel Horowitz, in the entryway of the couple's hilltop home, the sheriff's office said yesterday.

"We are still trying to determine the exact motive," Contra Costa County sheriff's spokesman Jimmy Lee told a news conference. "Although we have a suspect in custody, the investigation is still going on."

Mr. Lee said the arrest was made at 10 p.m. PDT Wednesday after investigators served two search warrants, but he declined to identify the youth or say what led to his arrest.

The announcement came just hours before a funeral for Ms. Vitale, who was killed Saturday. Mr. Horowitz discovered his 52-year-old wife's body in a mobile home where they were living while building their dream villa overlooking the oak-studded hills of Lafayette, a San Francisco suburb.

Quoting unnamed sources, the San Francisco Chronicle identified the suspect on its Web site and said authorities believe that the youth had an argument with Ms. Vitale after going to the property looking for marijuana-growing paraphernalia he had ordered using stolen credit card information.

The youth lives with his mother several hundred yards away, in a house with goats and chickens penned in the yard. Built with straw and solar energy, the house has been featured on East Bay tours of "green" homes. Yesterday afternoon, clothing and other belongings were piled on the front porch beneath a clothesline. No one answered the door.

Reached later at the house by phone, a man who identified himself as the owner's brother, David Curiel, said police had searched the home Wednesday night for a couple of hours but that the suspect apparently was at a relative's house.

Mr. Curiel said his brother and his family already were traumatized by the death of Ms. Vitale when the youth's home was raided. Asked about the suspect, he said, "I've met him. But he kept to himself."

Kurt Krikorian, a 19-year-old neighbor, said the suspect attended Acalanes High School, passed his high school equivalency test, then took some classes at a local junior college to keep himself occupied. High school officials declined to comment.

Mr. Horowitz, a criminal defense lawyer, specializes in white-collar, drug and death-penalty cases. Ms. Vitale worked part-time in his law office.

At the time of his wife's death, Mr. Horowitz was defending Susan Polk, who was accused of stabbing to death her therapist husband in their Orinda pool house. A mistrial was declared later in the high-profile case.