T.V. Turner, who patrolled Little Saigon as a Westminster cop for 14 years, said cultural barriers often made it difficult for detectives to crack cases.
"We went to cafe shootings where 20 people saw" what happened, Turner recalled, but "when you went to talk to them, they were all in the bathroom at the time.
"There's a lot of that still entrenched," he said.
The former policeman said the witnesses to Pham's beating could simply be afraid, or even getting pressure from elders not to step forward.
"They just don't want to ruffle up the feathers of a different group," he said. "It could be the parents are telling them, 'Don't get involved.' They just don't see any benefit to cooperating with police and going to court."
Turner pointed to the case of a Westminster officer, Anthony Duong Donner, arrested last August on charges that he acted as a lookout and enforcer for a Little Saigon businessman operating as a loan shark.
According to the FBI, the Vietnamese American officer threatened a woman who had borrowed money to open a coffee shop in Garden Grove and a lounge in Westminster, at an annual interest rate of 60%.
The woman complained that police would enter her business to intimidate customers and pull over employees after work, the FBI said. Donner, who patrolled Little Saigon, later admitted to collecting money while in uniform on his shift, the FBI said.
The distrust of police is especially powerful among first-generation Vietnamese immigrants. Though attitudes seem to have softened among later generations, Turner said, "a case like that raises its ugly head and that seems to give them validity in their old beliefs — they've got a reason still to mistrust the police."
Times staff writer Adolfo Flores contributed to this report.