Courtroom testimony appears to have solved the riddle of why tech journalist Rex Farrance was killed in a seemingly bizarre 2007 slaying: The thieves knew about all the pot stashed in his San Francisco Bay Area home.

Farrance's son Sterling, who had a medical prescription for the drug, insists he only had about 15 pot plants growing the attic; police, who long suspected narco-violence, have said it was more like 100 plants, and several pounds of processed bud.

Either way, word of the stash got out. Maybe Sterling, then 19, bragged to one too many friends. Accomplice Cleothius Termaine Amos, who turned state's witness in a plea deal, said he and three others went to the Farrance house looking for the pot:, only to find two bewildered parents.

After the couple couldn't cough up any money, the robbers pistol-whipped the woman and shot the man:

Amos said his group talked about the shooting afterward in the getaway car.

"Montrell was telling Little Man he was stupid, and why'd he have to shoot," Amos said. "And Little Man said he only shot him in the leg. And they were arguing back and forth and I was calling Little Man stupid, too."

The men had obtained a pound of marijuana from the house, which they sold for $1,800.