Michael Coombs said he was 17 when three Camden men "jumped him in," beating him relentlessly for 31 seconds as a high-ranking member of the Bloods street gang watched.

Soon afterward, Coombs was branded three times on his chest, a pattern like a dog's claw mark burned into his skin.

The beating and the branding were his initiation. In 2005, he became a Blood.

Coombs, now a Bloods outcast, testified yesterday against Corey Manderville, a Bloods member on trial in state Superior Court in a 2005 Camden killing.

Coombs' testimony offered a Camden County jury a rare look at the secret rules and codes that shape one of the country's most notorious gangs.

Coombs said he had always carried a weapon, had been taught to obey his superiors without question, and had paid weekly dues of $31 to the gang. He stood up and pulled down his shirt to show the jury the burn marks on his shoulder, to which Bloods members forcibly added a fourth when Coombs was ejected from the gang.

The number 31 has significance to the Bloods. In addition to the fees and initiation time, Coombs said, the gang lives by 31 rules.

Coombs got involved with the Bloods when he was barely a teenager, he said.

"I went looking for them," Coombs, who is serving a sentence for aggravated manslaughter. "They didn't come looking for me."

Coombs, of Pennsauken, is one of four men authorities allege were involved in the killing of Dewey Marshall, 22, who was gunned down in the doorway of his Camden apartment in a home invasion in August 2005.

When Coombs pleaded guilty to aggravated manslaughter in Marshall's death, he agreed to testify against others in the case. Lawrence Willis, a second man and a Bloods member, has also pleaded guilty in the slaying.

According to Coombs, Manderville was there, too, along with Earl Moore, who has not been charged in this crime but is serving time in state prison. Moore shot Marshall as Coombs watched from nearby, Coombs said, and Manderville and Willis stayed in the car the whole time.

Assistant Camden County Prosecutor Ira Slovin is arguing to the jury that Manderville went to Marshall's apartment as "backup," and that all four men were participants in the killing.

When Coombs was initiated in 2005, or "brought home," he said, he had already been working for years to show the Bloods he could be valuable. That work included selling heroin regularly, he said.

"Bloods members sell drugs, some rob and steal, some work and have jobs," he said.

After his initiation, Coombs became a foot soldier, the lowest on the Bloods' chain of command. That meant his loyalty was frequently tested, he said, and that was largely the reason he was told to approach Marshall's Ferry Avenue apartment on Aug. 29, 2005.

That night, after the four men smoked pot and surveyed the building for a while in the car, Coombs said, Willis ordered him and Moore to knock on Marshall's door.

"I was like, 'I'm not doing that. That's dumb,' " Coombs said yesterday. "But then [Moore] was like, 'You got to do it.' "

When Marshall opened the door, Moore tried to force his way in, Coombs said. Marshall pushed back against the door, causing it to break off its hinges. As Moore fired two shots, one of which hit Marshall in the head, Coombs did nothing, he said.

"I was in shock a little bit," he said. "For a couple seconds I just stood there."

The men drove away after Marshall fell to the ground. Two days later, Coombs said, he was punished for getting cold feet instead of helping Moore.

He said a group of men, including Moore and Willis, had forced him into a van and burned a fourth mark onto his shoulder with a cigarette - a symbol that meant he was no longer part of the gang.

"They said, 'You're lucky we don't kill you,' " he said.

Coombs, who was arrested in March 2006 in the killing, was also severely beaten in jail in the months after he agreed to testify in Manderville's trial. The attack, in which three inmates were charged, left Coombs in critical condition for several days. Relatives had said he had a shoe print on his face and bruises on his brain.

Testimony in Manderville's trial is expected to continue today.

Contact staff writer Allison Steele at 856-779-3838 or asteele@phillynews.com.