Feb 1 2023

Cocaine, Benzoylecgonine and drug driving

We all know that drink driving is a crime and has been for a very long time, but it is only within the past decade that drug driving has been a criminal offence in its own right – previously you could be guilty of drug driving but it was very difficult for the prosecution to prove and so hardly any prosecutions were brought.

Drug driving today is an offence contrary to section 5A of the Road Traffic Act 1988. There are a number of specific drugs that you must not use before driving. The one we are interested in today is Benzoylecgonine, which occurs if you use cocaine.

Why Benzoylecgonine?

Benzoylecgonine is a chemical created entirely inside your body as it breaks down cocaine. Benzoylecgonine does not have any intoxicating effect itself and is included in the prohibited list purely to crack down on cocaine use because it stays in your blood much longer than cocaine. Nonetheless, if you are found driving with it in your blood you will be disqualified from driving for at least 12 months – likely much longer.

Cocaine will be fully eliminated from your blood within a few hours of use. Benzoylecgonine can often be detected several days after cocaine was last used. Because Benzoylecgonine stays in your blood longer than cocaine, it is very common for cocaine users to be charged with drug driving because they were found to have Benzoylecgonine in their blood.

How is Benzoylecgonine detected?

Benzoylecgonine is typically detected in the blood using a method called liquid chromatography-tandem mass spectrometry (LC-MS/MS). This is a highly sensitive and specific analytical technique that allows for the precise measurement of drug concentrations in biological samples.

In LC-MS/MS, a blood sample is first extracted to isolate the Benzoylecgonine. The extracted sample is then injected into a chromatography column, where the Benzoylecgonine is separated from other components in the sample based on its chemical properties. The separated Benzoylecgonine is then detected and quantified using a mass spectrometer. The mass spectrometer ionizes the Benzoylecgonine and generates a characteristic mass-to-charge ratio (m/z) that is used to identify and quantify the drug.

LC-MS/MS is a widely used method for the detection of Benzoylecgonine in blood because of its high sensitivity, specificity, and ability to accurately measure low levels of the drug. This makes it well suited for forensic toxicology

Benzoylecgonine defences

The first think to recognise about Benzoylecgonine is that is can only be in your body if you have used cocaine! This means that you cannot passively or accidentally ingest Benzoylecgonine from another source.

The tap water defence myth

Before we look at defences, we should take a moment to dispel a myth that a few clients have brought up with us – apparently at the suggestion of other solicitors – that you can get Benzoylecgonine in your system by drinking tap water.

In 2014, a report by the Drinking Water Inspectorate made headlines and had newspapers claiming that cocaine was in tap water. What the DWI found was Benzoylecgonine. How much did they find? About 11 nanogrammes per litre of water! That means you would have to drink well over 4,500 litres of tap water in one go just to reach the drug driving limit! I’ve rounded that figure down, the “over” bit would be more than enough water to kill you if you attempted to drink it all!

Real Benzoylecgonine defences

Now we’ve dispelled the myth, let us move on to some defences that are actually worth thinking about.

The first thing to do is to decide whether we are saying that you have never used cocaine or that you have used it but not recently enough to put you over the limit. This is important because focuses our line of defence.

“I have never used cocaine” – Benzoylecgonine defences

If you have never used cocaine – or at least if you haven’t used it in years – then the Benzoylecgonine detected by the police cannot have come from you. This leaves three options: an error in the data handling procedures, the wrong sample has been tested; or the result was contaminated at the laboratory.

The first two options, data handling error or wrong sample tested, can be dealt with by early preparation. Always accept the portion of blood that the police offer you at the station and always have it tested independently by a reputable toxicologist. Doing this will highlight that an error has been made if the prosecution result comes back higher than yours.

Continuity errors

When we say “data handling error” what we really mean is that somebody in the laboratory has made a mistake, such as by looking at the wrong piece of paper when preparing a report or entering the wrong information from a label. This is something that should be double checked at the lab and is unlikely to  happen, but mistakes do occur.

How can the wrong sample be tested? This happens when people don’t check what they are doing. For example, if a police officer takes multiple samples from different people then muddles up the labels – it shouldn’t happen but I’ve seen some shockingly lax practice in my time. It could also happen if the bag that the sample is submitted in has the wrong label on or if samples become mixed up in transit. For example, we have had cases where a bag seal number on arrival doesn’t match that entered on dispatch. Or where a sealed bag has arrived open meaning anything could have happened to the sample.

Both of these can be detected by your solicitor carefully examining the continuity evidence. This means checking that the seal number given by the police officer at the point of taking  a sample matches that opened by the lab and that matches the sample ultimately tested. Mistakes do happen, just look at Synlab for evidence of systematic errors in their thousands.

Benzoylecgonine contamination

Your blood sample is not tested in isolation at the lab. It is tested as part of a batch of samples. That batch will include other blood samples as well as comparison test samples and blanks. Comparison test samples are effectively positive Benzoylecgonine tests that are made up by a lab technician to calibrate their results against. This means they add Benzoylecgonine to their comparison samples so they know how much is in each one. They can then calibrate the results of the real drug driving samples against the comparators. Because of this, there is always the possibility of contamination of the real samples or their results if the lab technician does not handle the comparison tests properly. To counter this risk, the lab uses blank samples. These are samples known to be free to Benzoylecgonine at the start of the test. If they remain free of Benzoylecgonine at the end of the test the lab will say that no contamination occurred.

Despite the impression you get from television, forensic testing is not infallible. Mistakes can, and do, happen. Those mistakes by technicians are usually picked up by the technician themselves, or by the reporting scientist, or by the peer reviewer. Still errors slip through, that is the nature of work conducted by humans.

We always have test results reviewed by an independent toxicologist who will review the work done by the lab and produce his own report. Our toxicologist will look for errors by the lab and point out places where they have altered the results (a very common issue) and say whether that alteration is scientifically justified or not. He will look for anything that suggests the result of the test are unreliable. In short, if you did not use cocaine and the lab has made a mistake, he will find it.

“The Benzoylecgonine reading is too high”

If you accept using cocaine but believe the level of Benzoylecgonine is too high for how much and when you used we need to consider another option. The points above about contamination can still be in play and it is always worth having a toxicologist review the prosecution evidence for signs of contamination. But, we also need to think about other potential explanations.

At London Drink Driving Solicitor, our ethos is all about giving you honest advice, which is why we have to say at this point that Benzoylecgonine can be in your blood a lot longer than you might think. If you used cocaine in the few days before the police blood tested you then there is a good chance that you will have Benzoylecgonine in your system. Nonetheless, if it really is high and a lot of time has passed then it may still be worth challenging.

The key challenge here is to look at how the blood sample has been treated. The police and lab will log the times they interact with you blood specimen. For example, the police will record when the blood is taken, what they do with it after taking it and when they do those things.

If blood is not stored properly then it can affect the reliability of the subsequent test result. This has two effects where cocaine is concerned. The longer blood is left, the lower the cocaine level will drop, but the Benzoylecgonine will increase. It does take a long time, one US study found an increase after 100 days of storage. That’s important in England and Wales where tests are frequently taking months to come back – in fact some have taken so long that the police have run out of time to prosecute! The increase is likely to be small but if you are only just over the limit it may be enough to put you back below the limit. If the reading is very high then a reduction may reduce the sentence you received. Of course, if evidence can be shown that the result of the test is unreliable then the court should exclude the result altogether.


There are many things that can go wrong when blood is tested by the police and, if you think the result is potentially wrong, then you should challenge the result.

Call us today for honest legal advice on Benzoylecgonine defences. You can speak to one of our expert solicitors on 020 8242 4440 or send us a message and we’ll get back to you.