Jaland Small was sitting in the right rear seat of Isaiah Pearson's car when it struck a culvert, fencing and then a tree near Taree in October 2017.

The boy, described by his family as bubbly and with a huge personality, died at the scene of head injuries.

For about 10 minutes prior, the car had been followed by Chief Inspector John Sullivan.

But he was never in a pursuit, as defined by police procedures, coroner Carmel Forbes found this week.

"Once he had lost sight of the vehicle, it is reasonable to conclude that he was no longer attempting to stop and apprehend the occupants, as the definition of a pursuit requires, but was instead trying to locate the vehicle.

She said the primary factor in Jaland's death was the manner of Mr Pearson's driving.

The then 20-year-old drove at excessive speed on an uneven road while significantly impaired by alcohol and without functioning headlights.

Chief Insp Sullivan, who began following the car after noticing it had no registration plates, was clearly aware of the pursuit rule book, the coroner said.

When asked if he was "making this a pursuit", the officer told police radio he was "following at this stage".

"Chief Inspector Sullivan turned his warning devices off shortly after turning onto Cedar Party Road (north of Taree) and did not attempt to keep in contact with the Nissan," Ms Forbes said.

"This action is again not consistent with an 'attempt ... to stop and apprehend' the vehicle."

Pearson, now 23, was convicted in 2018 of dangerous driving occasioning death aggravated by alcohol intoxication and disqualified driving, and jailed for six years.

He will be eligible for parole in April.

Pearson's licence was also disqualified until five years after his eventual release date. If he gets a licence, he will require an alcohol interlock for four years.

Australian Associated Press