A review of a police chase near Nelson last year that killed three people has found the fleeing driver had taken methamphetamine.
Frontline officers say they're encountering more and more paranoid drivers high on the Class A drug.
Mother-of-five Carmen Yanko was the innocent victim of the chase, killed while driving to work at the Nelson markets one morning last March.
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The fleeing driver, Johnathan Tairakena, was also killed, as was his passenger Phillip Stretch.
On Tuesday the Independent Police Conduct Authority (IPCA) review revealed Mr Tairakena was on drugs at the time, which police union boss Chris Cahill says is an increasing problem for frontline officers.
"The decision making when you are on methamphetamine, the paranoia and those sorts of things, stand to increase the bad decision to flee."
The review shows police were looking for a fugitive called Lewis Popata. Police had tried stop Mr Tairakena's car around 5.40am in the Richmond area, thinking it was him.
Instead it fled towards State Highway 6 at speeds of around 130km/h, and while overtaking a truck, smashed into Carmen Yanko head on.
A case of mistaken identity led to a triple fatal in just two minutes and 54 seconds.
The IPCA found: "Police were justified in commencing the pursuit, because they reasonably believed that Mr Popata was in the vehicle and that warrants had been issued for his arrest."
It also found the pursuit "was conducted in accordance with law and order policy".
The amount of methamphetamine out there in the community means there are a lot of people driving who will be affected," Mr Cahill said.
Methamphetamine is also suspected to have been used by Mongrel Mob member Astin Hooper in Kawerau last month. He fled police, and was shot dead after robbing a bank.
"There's no clear test around impairment, so we don't know the level of influence on the manner of driving," Mr Cahill said.
A major review of police pursuit policy is coming out this Friday. Meth-fuelled drivers are just one factor in an incredibly complex problem.