IR-01-26-18611
12 June 2026
Nigel Gray
[FYI request #34771 email]
Dear Nigel
Request for information
Thank you for your Official Information Act 1982 (OIA) request received 23 May 2026, in
which you asked for information regarding crash reporting. I have answered each part of
your request below:
I am requesting the following information regarding the classification of road
crashes as “drug-related”, “alcohol-related”, “medical-event-related”, or any
similar causal category used in official reporting, dashboards, or public
statements. This request arises from the contradiction between:
Agency statements that no single factor can be confidently identified as the
primary cause of a crash, and
The agency’s practice of classifying crashes into specific causal categories such
as “drug-related”.
To resolve this contradiction, I request the following information:
1. The decision rules used to classify a crash as “drug-related”
Please provide:
The criteria, thresholds, decision rules, or tests used to determine that a crash is
“drug-related”.
Whether toxicology detection alone is sufficient to classify a crash as
“drug-related”.
Whether impairment must be established, and if so, how impairment is
determined.
Whether causation must be established, and if so, how causation is determined.
Police does not apply fixed criteria, thresholds, or decision rules to classify a crash as
“drug-related.” For deceased drivers, any determination regarding drug involvement is
made by a coroner in the Coroners Court. For surviving drivers, Police rely on the
Police National Headquarters 180 Molesworth Street. PO Box 3017, Wellington 6140, New Zealand.
Telephone: 04 474 9499. Fax: 04 498 7400. www.police.govt.nz
outcomes of authorised testing processes, including oral fluid screening and laboratory
analysis of evidential blood samples.
The presence of a substance alone is not determinative of impairment or causation.
Police record factual observations, test results, and relevant circumstances within the
Traffic Crash Report (TCR). Any subsequent classification for reporting purposes is
undertaken by the relevant agency responsible for analysis, based on the totality of
available information. This aspect of your request is therefore refused under section 18(e)
of the OIA, as no such documents are held.
2. The process for moving a crash from “pending toxicology” to
“drug-related”
Please provide:
The workflow, internal guidance, or standard operating procedures governing this
change.
The roles or units responsible for making the classification decision.
Any quality-assurance or review processes applied before the classification is
finalised.
Within Police systems, a status such as “pending toxicology” may be recorded where test
results are outstanding. Once results are received, the TCR may be updated to reflect
this information. This update reflects the availability of additional evidence rather than a
discrete classification decision made under a formalised workflow.
There is no separate prescribed process, standard operating procedure, or designated
unit responsible for transitioning a crash from “pending toxicology” to “drug-related.”
Police update recorded information as new evidence becomes available, and any
subsequent classification for analytical or reporting purposes is undertaken externally,
including by a coroner or NZ Transport Agency Waka Kotahi (NZTA). This aspect of your
request is therefore refused under section 18(e) of the OIA, as the information does not
exist.
3. The evidential standard required to classify a crash as “drug-related”
Please provide:
The evidential threshold required (e.g., presence, impairment, contribution,
causation).
Any scientific, legal, or policy basis for this threshold.
Any documents that define or describe the difference between:
presence of a substance
impairment
causation
contribution
Police does not apply a defined evidential threshold for classifying a crash as
“drug-related,” such as presence, impairment, contribution, or causation. Police’s role is
to collect and record factual information, including observations, test results, and
investigative findings, without assigning a formal classification based on a prescribed
evidential standard.
Distinctions between the presence of a substance, impairment, contribution, and
causation are matters assessed by forensic specialists and, where applicable, a coroner.
Police does not hold specific documents defining these distinctions for the purpose of
crash classification, and this aspect of your request is therefore refused under section
18(e) of the OIA, as the information does not exist.
4. Reconciliation of the contradiction
Please provide:
How the agency reconciles the statement that “no single factor can be confidently
identified as the primary cause of a crash” with the practice of assigning crashes to
specific causal categories such as “drug-related”.
Any internal documents, emails, memos, or guidance that address this issue.
Police’s role in crash investigations is to establish and record the facts and circumstances
of each crash, rather than to attribute a single definitive cause. Officers assess each
crash based on the totality of available evidence and record relevant contributing factors.
No single factor is treated as determinative in isolation.
The distinction arises because Police provides factual inputs, while downstream
classification and aggregation into specific categories (such as “drug-related”) are
undertaken by agencies responsible for analysis, including NZTA, or through coronial
findings. Police does not hold internal documents reconciling this distinction in the terms
described, and this part of your request is therefore refused under section 18(e) of the
OIA.
5. Classification audit or accuracy checks
Please provide:
Any audits, reviews, or assessments of the accuracy, consistency, or validity of
crash-cause classifications.
Any documents discussing limitations, uncertainties, or risks associated with
assigning causal labels based on toxicology results.
Police does not hold audits, reviews, or formal assessments of the accuracy, consistency,
or validity of crash cause classifications where those classifications form part of national
reporting frameworks. Police’s role is limited to recording factual information,
observations, and investigative findings within the TCR.
To the extent that limitations or uncertainties exist, these relate to the availability and
timing of evidence, including toxicology results and witness accounts. Police records
information as it becomes available but does not hold standalone documents assessing
the risks or limitations of assigning causal labels. Accordingly, this part of your request is
refused under section 18(e) of the OIA as no such documents are held.
6. Historical or current definitions
Please provide:
Al definitions of “drug-related crash” used by the agency in the last 10 years.
Any changes to these definitions, including the dates and reasons for the changes.
Police does not hold formal definitions of “drug‑related crash” for classification purposes,
either current or historical. Police records observations and evidence relating to crashes
but does not apply standardised definitions, thresholds, or coding frameworks for
categorising crashes in this way.
Responsibility for defining and applying classification categories for national reporting
purposes, including any changes over time, rests with external agencies such as NZTA.
Accordingly, this part of your request is refused under section 18(e) of the OIA, as the
requested information is not held by Police.
In addition, Police acknowledges that there are limits to both the information it holds and
the determinations it is authorised to make in relation to fatal crashes. Police’s role is to
investigate crashes and record factual information obtained through those investigations.
Police is not the statutory authority responsible for determining the medical or legal cause
of death, which is a matter for a coroner. Similarly, agencies such as NZTA may
undertake their own analysis or apply classification frameworks for reporting purposes
that are outside Police’s control. Should you seek further information regarding the formal
determination of cause of death or the application of reporting classifications, you may
wish to contact the Office of the Chief Coroner or other relevant agencies directly.
If you are not satisfied with the way I have responded to your request, you have the right
under section 28(3) of the OIA to ask the Ombudsman to review my decisions.
Information on how to do this is available online at
www.ombudsman.parliament.nz.
Yours sincerely
Inspector Peter McKennie
Acting Director: Road Policing
New Zealand Police
