Deputy coroner Harriet Grahame on Friday made 28 recommendations - including a pill-testing trial - after a lengthy inquest into six MDMA-related deaths at music festivals.

Ms Grahame said medically supervised drug checking wasn't a magic solution but she was in "no doubt whatsoever" there was sufficient evidence to support a trial.

But Mr Fuller on Monday said NSW Police didn't support pill testing.

"I'm gravely concerned about the message that pill testing sends to young people about the consumption of illegal substances," he said in a statement.

"Pill testing provides a false confidence to an individual that the drug they want to take is safe.

"There is no such thing. All illegal substances carry the risk of harming or ultimately killing the user."

The commissioner cited evidence from NSW chief health officer Dr Kerry Chant that most of the harm from taking illicit substances did not come from contaminants.

"Most of the harm occurs from drugs people intended to purchase. Pill testing will not reduce this harm," Mr Fuller said.

"At present, the technology does not allow for adequate identification of dose levels or small traces of highly toxic substances."

The testing method is also an inaccurate reflection of the entire composition of the pill, he added.

"These are some of the critical flaws in proposals to test pills at dance parties and music festivals and as such, any such proposal will not be supported by me."

Mr Fuller said NSW Police remained committed to reducing harm by targeting supply networks and organised crime and through supporting harm minimisation strategies including education.

Premier Gladys Berejiklian has long refused to back pill testing and on Friday insisted: "We have a strong view that pill testing is not the way."

Australian Associated Press