SAN DIEGO -- A Carlsbad man who testified that he "snapped" and killed his on-again, off-again girlfriend last summer when he found flirtatious text messages on her cell phone was convicted Monday of first-degree murder.

Jurors were in their fourth day of deliberations when they reached their verdict against 41-year-old Jonathan Scott French, who maintained he was guilty of voluntary manslaughter, not murder.

The medical supplies salesman faces 26 years to life in state prison for the July 31 slaying of Jennifer Stark, a court reporter at the Vista Courthouse.

Retired Judge Peter Spinetta scheduled sentencing for July 12.

Jury foreman Scott Williford told reporters that French thought about what he was doing and took awhile to get up the nerve to kill the 43-year-old victim.

"The evidence (showed) that he'd gone to her, taken a knife, gone through several drawers to find the right knife, come back, and there were several slits on her throat before he decided to kill her," the juror said.

Lead prosecutor Jeff Dusek said the victim's family has gone through agony.

"Her parents, her children, her friends, her co-workers ... they suffered tremendously because of what happened," he said. "It's something that could happen to any one of us. By all accounts, Jennifer Stark was a terrific lady, dating this fellow, and it went bad, it went real bad. It was just agony for everybody; a ripple effect throughout her entire life."

Stark's friend, Kate Powers, said the guilty verdict means some closure for Stark's two teenage children.

"This has been the most horrendous ordeal, for all of us, her family, her friends, a lot of people in the community," she said. "We are pleased with the verdict. We miss Jenny. We think about her every day. She was a beautiful human being that will be truly missed."

Dusek said French planned the murder and carried it out by beating and choking Stark and slicing her throat after they returned to her Carlsbad residence following a night of drinking and kissing.

Defense attorney Kenneth Kaminski told the jury that French killed Stark in the heat of passion and should be convicted of voluntary manslaughter.

French, testifying in his own defense, said it wasn't anger that caused him to punch Stark after reading "flirtatious and suggestive" text messages from another man.

"I just absolutely snapped," the defendant said. "I went from zero to a thousand."

French said he felt rage like he had never felt before and hit Stark, sending her to the ground.

"I screamed at her, why?" the defendant testified.

French said he hit Stark a few more times and grabbed the unconscious woman by the neck. The defendant said he grabbed a knife, but didn't really remember slicing Stark's throat.

French testified that things between him and Stark seemed to be going very well after the two got back together following a trip he took to Spain.

As they kissed in her home before the killing, the subject of a "goodbye" letter that he had written before his trip came up, the defendant testified.

He testified that Stark told him that she had called him twice regarding the letter while he was overseas, and pulled out her phone to prove it.

French said he saw a name on the phone -- Chris -- that he had never seen before, and questioned Stark about it.

When French yelled, "Are you still seeing him?" Stark responded, "What if I am," the defendant said upon questioning by his attorney.

After he killed Stark, French said he tried to cut his wrists and stabbed himself in the leg in an attempt to kill himself. He said he drove around until turning himself in at the Encinitas sheriff's substation.

On cross-examination, Dusek asked the defendant why he wasn't successful at killing himself.

"There's a rage there," French said. "It wasn't there anymore."

"Your intent was the same, wasn't it? Dusek asked.

"I just wasn't very successful at it," French answered.

"Why didn't you do it?" the prosecutor asked.

"It's harder to kill yourself than you think," the defendant answered.

French said he and Stark had been through numerous break-ups and reconciliations from the time they met in the fall of 2006. The defendant said they bought a house together, but it went into foreclosure when his real estate appraisal business went south.

Stark's 15-year-old son found her lifeless body in a pool of blood in a hallway upon returning home about 11 p.m.

Dr. Jonathan Lucas testified that Stark suffered at least 14 distinct slice wounds to her neck -- which was fractured -- and was also beaten about the face and choked into unconsciousness.

The fatal blow was a 5 1/2-inch cut to the front of the victim's neck that went all the way to her spine, the deputy medical examiner said. He said the wound went through the carotid artery and jugular vein and cut across Stark's airway and esophagus.

The deputy medical examiner said Stark's nose was broken and she had 15 separate injuries -- which included 10 impact wounds -- on her face, along with bruises on her shoulder, collarbone, right breast, arms, hands, feet and head.

Because Stark worked for the county court system, Spinetta -- a retired Contra Costa County judge -- was assigned to hear the case in San Diego.