The superstar Michael Jackson said that he did not have a drug problem, the Los Angeles court heard.
Police detective Orlando Martinez said that Jackson's mother Katherine had told him that the family tried drug interventions for the singer.
The testimony came under questioning by lawyers for concert promoter AEG Live, which is being sued by Katherine Jackson for negligence in the star's death.
Mr Martinez, who led the investigation into Jackson's death in June 2009, said he first interviewed his mother at the hospital.
But six months later, he decided to go back to her and check out "some things regarding family meetings about addiction".
He said it was then that she told him about several attempts by the family to hold interventions and get Jackson into rehab.
"Mrs Jackson said the family tried to help him but he would have nothing to do with it," Mr Martinez said.
"She had asked Michael if he was taking any drugs, and he denied it."
He said Katherine Jackson told him she believed her son was taking medicine for back pain and might have become addicted.
"What did Mrs Jackson tell you?" asked AEG lawyer Marvin Putnam.
"The family attempted several interventions," said the detective.
"She had talked to her son about drugs herself."
She said the efforts produced no results, Mr Martinez said, because "he denied having a problem".
Katherine Jackson also told him that the first time she ever met Dr Conrad Murray was at the hospital the day her son died.
Murray was convicted of involuntary manslaughter after giving the anaesthetic propofol to the pop star. Bottles containing pain killers were found in the singer's bedroom.
Earlier, Mr Martinez said that five days before Jackson died, his manager called the singer's doctor, told him Jackson was sick, and implored him to have blood tests done, according to a voicemail played in court.
The message left by Frank Dileo was retrieved by police from Murray's mobile phone.
"I'm sure you're aware he had an episode last night," the message said. "He's sick. ... We gotta see what he's doing."
Katherine Jackson's lawyer Brian Panish acknowledged outside court that the episode occurred on the day Jackson was told by Kenny Ortega, the director of his This Is It concert, to go home from a rehearsal because he was pale and shivering.
Mr Panish suggested that if Mr Dileo was aware of the incident, so were AEG executives. Jurors were not given any further details on the episode.
Katherine Jackson's lawsuit claims AEG did not properly investigate Murray.
AEG denies it hired the doctor, and it is likely to blame Jackson for insisting on having Murray as his doctor because of his dependence on propofol, which Jackson used to sleep. The company alleges Jackson was addicted to numerous drugs.