A breathalyser test was carried out ninety minutes after the stop. The result: 0.52 per mille. The line between a misdemeanour and a criminal offence runs at 0.5 per mille. Does that mean the driver’s concentration was above 0.5 per mille at the time of driving? Not necessarily. And this is precisely where a toxicology expert’s opinion can open up room for a defence.
What Retrospective Calculation of Blood Alcohol Concentration Involves
A retrospective blood alcohol calculation is an opinion produced by a forensic toxicologist which, on the basis of known parameters – the time and result of the test, data about the alcohol consumed, the driver’s weight, sex, the time of consumption and of the last meal – calculates what the driver’s probable blood alcohol concentration was at the time of driving, not at the time of the test.
The body eliminates alcohol at a rate of between 0.10 and 0.20 g/kg/h (the so-called β-60 elimination coefficient). If the test was carried out one hour after the stop and showed 0.52 per mille, then depending on the individual elimination rate the concentration at the time of driving could have been either below or above that figure. The expert calculates a range of probable values, taking into account the margin of error.
When This Approach Can Be Effective
The test was carried out with a significant delay. Where sixty, ninety or more minutes elapsed between the stop and the test, the difference between the test result and the concentration at the time of driving can be material – particularly where the driver was in the elimination phase, meaning the blood alcohol concentration was steadily falling.
The result is close to the misdemeanour/criminal offence threshold. At a reading of 0.51–0.55 per mille, every hundredth of a per mille has legal significance. The criminal offence under Article 178a of the Criminal Code begins at 0.5 per mille – if the expert calculates that the concentration at the time of driving may have been below that threshold, the court may apply the in dubio pro reo principle and classify the conduct as a misdemeanour under Article 87 of the Code of Misdemeanours. The consequences are then considerably less serious: a fine rather than a conviction, and a shorter driving disqualification.
The driver claims to have drunk only after the drive. Where alcohol was consumed after the journey ended, the expert can assess – on the basis of the time of consumption, the amount consumed and the test result – whether such a version of events is physically possible. In cases where the prosecution cannot exclude this, the in dubio pro reo principle operates in the defendant’s favour.
The driver drank the previous evening and was stopped the next morning. Following heavy alcohol consumption the previous evening, alcohol can remain in the blood the following morning. The expert can assess what concentration the driver may have had at a specific hour, taking into account the amount consumed and the time elapsed since consumption.
What the Expert Takes Into Account
A retrospective opinion takes into account the driver’s weight, height and sex (which affect the volume of alcohol distribution), the type and quantity of alcohol consumed, the time of consumption and of the last meal (food slows absorption), the test result and the precise time it was carried out, the phase of alcohol kinetics (absorption versus elimination) and the individual β-60 elimination coefficient.
The standard range for β-60 is 0.10–0.20 g/kg/h – the expert applies both extremes to establish the range of possible concentrations at the time of driving. The greater the uncertainty in the input parameters, the wider the range and the greater the prospect of the in dubio pro reo principle applying.
How Courts Approach This Method
Retrospective blood alcohol calculation is a recognised forensic method, regularly applied in Polish courts. Courts are cautious, however – the expert’s opinion must be precise, based on solid input data and methodologically sound.
The opinion alone is not enough. It must be supported by the driver’s account of the quantity and timing of alcohol consumption, statements from any witnesses, medical data where the driver has a condition affecting alcohol metabolism such as diabetes, and any other documentation capable of corroborating the version of events. The better the factual basis is documented, the more persuasive the opinion.
When This Approach Makes No Sense
Where the test was carried out almost immediately after the stop, the difference in concentration will be minimal and no expert opinion will materially change that. The method is also of no use where the result is unambiguously high and far from any legal threshold. It carries a cost – obtaining a private toxicology opinion runs to several thousand zlotys – so the decision to commission one must be preceded by a realistic assessment of the prospects.
When to Act
As early as possible – ideally at the pre-trial stage. An application for a toxicology expert to be appointed can be submitted to the prosecutor during the investigation. The earlier the expert receives complete data, the more precise the opinion.
It is also worth noting that a privately commissioned expert’s opinion, although treated as private evidence, can effectively challenge the findings of the expert appointed by the court or prosecutor and form the basis for an application for a further expert to be appointed.
Contact Us
If you have a drink driving case and the test result is close to a legal threshold, or the test was carried out with a significant delay, it is worth discussing with a lawyer whether a retrospective toxicology opinion could change the outcome of your case.
It pays to be properly prepared: both in knowing what you can claim and in having a clear strategy.
We handle cases for drivers in Poznań and across the Wielkopolska region, with in-person and online consultations available for clients elsewhere in Poland.
Adwokat Marta Krzyżanowicz and Adwokat Michalina Koligot Law Firm “Adwokat dla Kierowców w Poznaniu”
ul. Adama Mickiewicza 18/3, 60-834 Poznań
tel. +48 795 001 536 · +48 531 335 713
kontakt@adwokatdlakierowcy.pl · www.adwokatdlakierowcy.pl
This text is for general information purposes only and does not constitute legal advice. Every case requires individual analysis.
