ACT Policing senior officer Rohan Smith said there were negative outcomes in using sniffer dogs at festivals, including that pills would be thrown on the ground and not noticed until well after the event.

"Children may see them as a lolly on the ground," Detective Superintendent Smith told the NSW Coroners Court on Thursday.

There were also concerns the sight of sniffer dogs at festival gates could lead people to take all of what is in their pocket to avoid arrest.

"That could have an adverse effect on their immediate wellbeing," Det Supt Smith said.

The use of sniffer dogs at music festivals has been a key issue for the inquest into six MDMA-related deaths at recent music festivals, in light of evidence suggesting one victim - Alex Ross-King - consumed multiple pills at the gates for fear of arrest.

Sniffer dogs couldn't differentiate drug suppliers from consumers, who would make up the majority of people detected at festival gates, Det Supt Smith said.

He said police in Canberra instead focused on identifying and arresting suppliers before large events, and by having high-visibility patrols to deter the sale of illicit substances inside festival grounds and building trust with patrons.

"We want them to trust us, especially when they have a friend in need," he said.

"We want to help them first, not deal with policing."

The 27-year policing veteran, who currently sits on a panel considering the future of pill testing trials in Canberra, raised concerns about another proposal - amnesty bins - due to potential security issues.

The inquest also heard NSW needed more research to understand the ways perceptions of dosage and purity changed how people took pills and tablets.

NSW Chief Health Officer Kerry Chant said it was important to focus on dose in their messaging to young people.

British academic Fiona Measham told the inquest she'd noted an "astonishing" four-fold increase in the amount of MDMA per pill or capsule.

But consumers being unaware of the change was "really problematic", the criminologist said on Thursday.

"If you give people the information, they'll take it on," she said.

The inquest is due to close on Friday.

Australian Associated Press