Prosecutors have presented evidence of the gang affiliation of the man on trial for the killing of high school athlete Jamiel Shaw, Jr. -- as they try to explain the motive.

Pedro Espinoza could face the death penalty if he's convicted and jurors agree the murder on March 2, 2008, was motivated by his gang ties.

One witness, a former Shaw neighbor, says as part of a police sting days after the killing, Espinoza smiled and said, "B.K. all day," after being prompted about the murder.

"B.K.," prosecutors explained, stands for "Blood Killer," and again pointed out the tattoo with those initials behind Espinoza's left ear.

Later, a man from Culver City described how he was confronted by Espinoza in a park a few months before the Shaw murder.

After Espinoza asked him 'where are you from?' -- Samuel Duran said he watched Espinoza ride his bicycle through the park and confront others.

"That's when he started throwing up his gang signs -- eighteenth street," Duran said.

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