Lamar Odom is recalling his own experiences with street drugs in the wake of Liam Payne's toxicology report ... telling us the substances could have made the late singer hear voices.
We got Lamar in Encino, CA and our photog asked if he had ever used the drug cocktail known as "pink cocaine" ... a mix of ketamine, methamphetamine and ecstasy that police say was found in Liam's system.
Lamar, a recovering addict who owns Odom Recovery Group, said he's done every drug Liam had in his body ... including cocaine and crack, which Lamar feels is the worst one.
In Lamar's expert opinion, these illicit drugs may have played a role in Liam's death ... namely, by possibly making him hallucinate.
That jibes with one police theory regarding Liam's fatal fall from his hotel suite balcony on the third-floor of the CasaSur Palermo Hotel in Buenos Aires.
Lamar says when he was using, he would hear voices in his head ... and he thinks that could have happened to Liam here too.
Liam, as we first reported, had been telling people earlier this year he was sober after past addictions to drugs and alcohol during his time with One Direction ... but, he was on what cops say was in the toxicology report, to which Lamar says Liam was "really scoring."
Lamar's got a lot of life experience here, and he's helping people stay sober these days ... so he's hoping Liam's death serves as a wake-up call for lots of folks, including celebs in Hollywood.