From Breath to Saliva: Is Evidential Drug Testing Moving to the Roadside?

For decades, roadside enforcement has followed a familiar divide. Alcohol can be measured quickly, while drug testing is a more complicated chain: screen the driver at the roadside, take them elsewhere for an evidential sample, send that sample to a laboratory, and wait for the result. In the United Kingdom, that divide is beginning to look less permanent.

In July 2026, Merseyside Police became the first UK force to deploy evidential roadside alcohol testing, allowing officers to obtain an evidential breath result without first taking a suspected drink-driver into custody for another test. The operational logic is simple: test closer to the moment of driving, reduce delay and avoid losing useful evidence while the body continues to metabolise alcohol.

For drugs, the UK is not there yet. But the policy conversation has moved significantly. The Department for Transport has now consulted on whether oral fluid, saliva and other alternative specimens could play a role in forensic drug-driving analysis, while the government has also supported exploratory work on a Mobile Evidential Drug Testing Instrument demonstrator. In July, ministers confirmed that the consultation responses were being considered and that no decision had yet been taken on introducing roadside evidential drug testing in England and Wales.

That distinction matters: evidential roadside drug testing is not currently the UK system. But for the first time in years, the question is being asked very openly. And at SafePAS, we believe it is the right question.

Why does the UK still rely on blood for drug-driving evidence?

The current system makes sense when viewed through the history of forensic toxicology. Under Section 5A of the Road Traffic Act, England and Wales have specified limits for controlled drugs in blood. Roadside oral-fluid kits can currently be used to screen for drugs such as cannabis and cocaine, but where a drug-driving case proceeds, the evidential framework for specified-limit offences relies on laboratory analysis of blood.

Blood has important analytical and legal advantages. Decades of research, established thresholds, validated laboratory methods and an extensive regulatory framework sit behind it. A result intended to support a criminal prosecution must withstand scrutiny in a way that a simple screening result does not.

But blood also creates an operational chain that is difficult to ignore. A driver must first be stopped and screened. If the case proceeds, obtaining the evidential sample may require transport, custody procedures and the availability of an appropriate medical professional. The sample then enters a forensic laboratory system that is serving many cases simultaneously.

The UK government itself now acknowledges the consequences. Its recent consultation states that the number of forensic blood samples required for drug-driving investigations has increased notably and that this has created significant challenges in both cost and forensic capacity. It also notes cases in which blood could not be obtained for medical reasons or because an approved medical practitioner was unavailable. So the debate is not about whether blood analysis works. It does.
The question is whether every part of the current process still needs to depend on it.

Waiting months for a drug-driving result is not a theoretical problem

The most striking weakness of a laboratory-dependent system is time. Not every UK drug-driving blood sample takes months to analyse, and turnaround times vary substantially between police forces and forensic providers. But publicly disclosed police data show very clearly that month-scale waits have been a routine part of the system.

Metropolitan Police data released under Freedom of Information legislation show that, in 2023, 1,423 of 2,055 blood samples from suspected drug-impaired drivers took between three and six months to return a result. During the first half of 2024, 650 of 915 recorded samples took between one and three months.

The picture is not identical everywhere, but it is not confined to London either. West Yorkshire Police reported that, among its 2025 year-to-date cases included in an October 2025 disclosure, 288 results took between one and three months, compared with 366 returned within one month. Historical West Yorkshire data also show periods when hundreds of cases took three to six months. South Yorkshire Police disclosed a similar pattern: in its 2025 data available by late September, 154 results took one to three months, while earlier years included substantial volumes in the three-to-six-month category.

These numbers should not be read as a single national turnaround-time statistic. They come from different forces, periods and forensic providers. But they demonstrate something more important: waiting months for toxicology results is a documented operational reality, not an edge case invented for a technology sales pitch.

That delay affects more than administrative efficiency. A case remains unresolved. Police resources remain committed. A suspect remains in a period of uncertainty. Evidence moves through custody, transport and laboratory workflows. The forensic system carries the cost of analysing every sample that reaches it. When thousands of drug-driving cases are involved, time becomes infrastructure.

Why saliva changes the economics of the problem

Oral fluid is already familiar to UK policing because it is used for roadside drug screening. The larger question is whether it can move beyond preliminary screening and support more of the analytical process itself.

There are obvious operational reasons to explore the idea. Saliva can be collected close to the roadside without the same process needed to obtain blood. Collection can be observed. It does not inherently require a venous blood draw, transportation to a medical setting or the same dependence on a doctor or other qualified professional simply to obtain the specimen.

The government has explicitly invited views on alternative forensic procedures involving oral fluid, saliva and sweat precisely because of cost, capacity and sample-collection challenges in the existing system. It also acknowledges that any alternative would require scientific evaluation, a cost-benefit assessment and legislative change before operational introduction.

At SafePAS, our position is clear: we support moving much more drug analysis to oral fluid wherever the science, validation and legal framework allow it.

Not because saliva should magically make forensic standards disappear. The opposite is true. If an oral-fluid result is going to carry greater evidential weight, the analytical requirements have to become stronger.
A binary roadside result — positive or negative — is not enough for that future.

Screening and evidential analysis are not the same thing

This may be the most important distinction in the entire debate.

A conventional roadside drug screen answers a deliberately limited question. Has the test detected a signal associated with a particular drug or drug class above its screening cut-off?

That can be extremely useful for preselection. But an evidential system has to answer much harder questions. Which substance is present? At what concentration? How reliable is the measurement? What quality controls were applied? How is the result recorded? How is the sample linked to the individual tested? What uncertainty is associated with the measurement? How does that result relate to the threshold defined by law?

Those are not simply engineering questions. They involve toxicology, validation, regulation, police procedure and legislation.

The complexity is visible in the current blood framework itself. In June 2026, the UK Forensic Science Regulator published updated guidance for Section 5A toxicology analysis following work to address scientific and quality challenges in drug-driving analysis. The requirements cover the analytical processes used to determine whether specified drugs are present in blood and at what concentration. Roadside evidential testing cannot succeed by lowering that bar. It succeeds only if analytical capability outside the traditional laboratory becomes good enough to meet it.

Alcohol may be showing where drug testing goes next

The timing of the UK debate is particularly interesting because alcohol enforcement has just provided a real operational example.

When Merseyside Police introduced evidential roadside breath testing in July, the force explained that the traditional journey from roadside screening to an evidential sample in custody could itself create problems. Alcohol continues to be metabolised while a driver is transported and processed, meaning the later evidential result may differ from the situation when the driver was first stopped. Moving the evidential measurement closer to the roadside reduces that delay.

Drugs are analytically much more complicated than alcohol. Different substances have different pharmacokinetics. Legal thresholds differ. The relationship between oral-fluid and blood concentrations is not uniform enough to simply replace one number with another. There is no reason to pretend that a drug analyser is just a breathalyser with a different sample.

But the operational principle is worth examining:

If the information matters most at the moment of enforcement, how much of the analytical process can responsibly move closer to that moment?

The Department for Transport is now asking a version of exactly that question. In its July parliamentary response, it confirmed that the current specified-limit evidential framework relies on blood while also acknowledging exploratory work on roadside evidential drug-testing capability, including the MEDTI demonstrator. A separate ministerial answer confirmed that oral fluid and saliva are among the alternative specimens being considered.

The idea is not entirely new. The Department for Transport published an expert-panel review of oral fluid and other alternative biological matrices for evidential drug-driving use as far back as 2017. What has changed is the operational pressure surrounding the question.

What would a future saliva-based roadside system need to deliver?

If the UK eventually moves toward evidential oral-fluid drug testing, the challenge will be much bigger than producing a faster positive result.

A credible system would need validated substance-specific analysis, quantitative measurement where the legal framework requires concentration, reliable internal controls, well-defined limits of detection and quantification, documented sample handling, secure reporting, operator training and a regulatory approval process capable of maintaining public confidence.

It would also require policymakers to determine what an oral-fluid concentration actually means legally. The current Section 5A framework is built around specified concentrations in blood. Oral fluid cannot simply inherit those numerical thresholds. Scientific evidence, operational validation and legislation would have to establish the relationship between the measured result and the offence being enforced.

This is why SafePAS does not argue that a device can simply be placed in a police vehicle tomorrow and replace the existing UK blood-testing system.

We argue that the work required to make that future possible should accelerate now.

Where Drug Hunter fits into that future

Drug Hunter was developed around a different proposition from conventional binary roadside screening. The system analyses oral fluid and provides substance-specific, quantitative information for selected drugs rather than only reporting a broad presumptive positive.

That does not currently make Drug Hunter an approved evidential replacement for blood testing in England and Wales. We think it is important to say that explicitly.

But it does mean that the technological direction of Drug Hunter aligns closely with the questions UK authorities are now asking. If the next generation of roadside drug testing must provide more than a yes-or-no answer, then portable quantitative oral-fluid analysis becomes increasingly relevant.

SafePAS is therefore actively participating in this wider transition. We are preparing technical and policy-oriented white papers, developing the analytical platform and working on the device and validation requirements needed to demonstrate how quantitative saliva analysis can be used closer to the roadside.

Our goal is straightforward: help make scientifically robust saliva-based drug analysis operationally usable as soon as the regulatory and legal framework is ready for it.

That means working not only on the instrument, but also on the evidence around it. It means engaging with law-enforcement professionals, forensic specialists, policymakers and potential partners. It means defining where on-site analysis can replace unnecessary steps and where laboratory confirmation must remain. And it means being clear about the difference between what is technically possible today and what must still be validated before it can become part of an evidential system.

The savings are potentially bigger than the test itself

It is tempting to evaluate a new roadside drug-testing system by comparing the price of one device with the cost of one laboratory analysis. That misses the larger system.

A blood-dependent workflow includes the officer’s time, transportation, custody or clinical procedures, the person qualified to collect the sample, consumables, forensic logistics, laboratory capacity, administrative processing and the delay before a result returns.

The UK government’s own consultation identifies both cost and forensic capacity as reasons for reconsidering the current approach.

Moving suitable analysis to saliva and closer to the roadside therefore has the potential to save much more than laboratory fees. It can shorten the chain between suspicion and information. It can reduce dependence on scarce medical and forensic capacity. It can allow laboratories to focus resources on cases that genuinely require advanced confirmatory analysis.

The exact financial impact must be established through proper pilots and cost-benefit analysis. But when a system currently sends large numbers of specimens through workflows that can take weeks or months, reducing unnecessary steps has value before the first laboratory invoice is even counted.

Faster does not mean less rigorous

There is an understandable concern whenever forensic analysis moves outside a laboratory: are we trading quality for convenience?
That must not be the model.
The future should not be fast instead of reliable. It should be reliable without avoidable delay.

Forensic laboratories will continue to have an essential role. Complex cases, disputed findings, emerging substances, confirmatory analysis and specialist interpretation will still require sophisticated laboratory infrastructure and expertise.

The opportunity is to stop treating the laboratory as the only place where meaningful quantitative drug information can exist.

Portable analytical systems are becoming more capable. Regulators are looking more closely at how drug-testing devices should be validated and controlled. Police forces are searching for ways to reduce delays. The UK government is openly considering alternatives to blood for drug-driving forensic analysis. Those developments point in the same direction.

The next question is no longer whether drug testing can happen at the roadside

Drug screening already happens there every day.
The more interesting question for the next decade is how much further roadside analysis can responsibly go.

Can officers receive substance-specific quantitative information at the point of testing? Can oral fluid eventually support evidential decisions? Can unnecessary blood collection be reduced? Can forensic laboratories be reserved for the cases where their capabilities add the most value? Can a process that sometimes takes months be redesigned around information available within minutes?

The UK has not answered those questions yet. And it should not answer them before the scientific, legal and operational evidence is ready. But asking them is already a significant change.

At SafePAS, we strongly support the direction of travel. We believe oral fluid can become far more important in drug-driving enforcement, reducing time and cost while bringing meaningful analytical information closer to the moment when police need it.

We are working to help build the evidence, methods and technology required to make that possible.

The roadside drug test of the future should not simply tell an officer that something may be there.

It should tell them what is there, how much is there, and what the next step should be based on reliable data.

And it should do that while the decision still matters.

FAQ

Does the UK currently use saliva as evidential proof for drug-driving offences?

Not for the specified-limit offence in the same way blood is currently used. Roadside oral-fluid devices can be used for screening, while the current evidential framework for specified-limit drug-driving offences relies on blood analysis. The government is considering possible future alternatives, but no decision to introduce roadside evidential drug testing has yet been taken.

Is the UK considering replacing blood with saliva for drug-driving analysis?

The Department for Transport has consulted on the potential use of alternative specimens including oral fluid, saliva and sweat for forensic drug-driving analysis. The responses are currently being considered. Any change would require scientific and operational evaluation and changes to legislation.

How long can UK drug-driving blood-test results take?

There is no single national waiting time, and performance differs between forces and forensic providers. However, police FOI data document many cases taking one to three months and, in some periods, three to six months. Metropolitan Police data for 2023, for example, recorded 1,423 of 2,055 samples in the three-to-six-month category.

Would saliva testing eliminate forensic laboratories?

No. Complex and disputed cases, specialist analysis and confirmatory testing would continue to require laboratory expertise. The potential benefit is to move appropriate analysis closer to the roadside and reduce unnecessary dependence on centralised laboratory workflows.

Is Drug Hunter approved as an evidential roadside drug-testing device in the UK?

No. Drug Hunter should not currently be presented as an approved replacement for UK evidential blood testing. SafePAS is developing quantitative oral-fluid analysis technology and supporting the scientific and policy work needed to explore a future in which more drug analysis can take place directly at the roadside.

What is SafePAS doing in this area?

SafePAS supports the transition toward validated quantitative oral-fluid analysis. The company is preparing technical and policy white papers, developing its analytical platform and devices, and working to demonstrate how substance-specific quantitative saliva testing could support future roadside workflows.

Useful links
1. https://www.merseyside.police.uk/news/merseyside/news/2026/july-2026/national-first-as-merseyside-police-deploy-evidential-roadside-drink-driving-technology
2. https://questions-statements.parliament.uk/written-questions/detail/2026-07-09/17402
3. https://questions-statements.parliament.uk/written-questions/detail/2026-07-13/18369