Back calculation on alcohol blood sample

Convicted Driver Insurance

Barp

New Member
HI All,
Been following these threads for quite some time and really appreciate all your honesty and support.
I'm very. V confused about the back calculation, involved in a bump a couple of weeks ago and really struggled to do the breatherlyser, police very helpful and just happened to be passing. A couple of my airbags went off so managed to get car off the road. Other driver left very quickly having given contact details etc. This bump really shook me up and as the air bags had gone off the police said they needed to get an alcohol reading but also needed to take me to casualty. Arranged for blood test, taken about 3 hours after accident, have sent my sample off and have a reading of 50, spoke to the doctor who did the test and he said all should now be OK as under the limit. I have since been told some police forces routinely do back calculations, is this true or only for serious accident?
Any info greatly receives, thanks
 
It seems that police forces are less likely to do back calculations routinely, and particularly where there has been no third party injury.
For them to do a back calculation they would need to interview you to ask for your height, weight, when you last drank and what plus other questions.
Even if they did do a back calculation, the closer the result would be to the legal limit, the less likely it would be that they would prosecute because it is not an exact science, just a best estimate within a range. Your answer, dependant on the questions that I listed above, would be close to the legal limit so I doubt that they would try to secure a conviction even if they did try a back calculation.
if the police do contact you to do an interview at the police station then you should ask for the duty solicitor to be present and seek advice from him / her as to how you should answer the questions.
 
Thank you, would the police wait for the bac reading to be sent to them before requesting a back calculation? Was released without bail, dearrested and given PCs contact details. Only paperwork given was about receiving sample to have analysed, just very frightened and confused, what would be the worse case timeline? Really appreciate your insight
 
If there had been serious injury, because there had been a 3 hour delay I would have expected the Police to interview you that day to ask you questions.
There is still the scope now to ask you for an interview but I would expect then to wait until they got the result, which will take about 6-8 weeks.
What is in your favour is that whilst you have been given a reading of 50, unless your laboratory say otherwise that is the exact result, whereas for the police the laboratory get their result, deduct 6 and say “not less than XX......” so 44 in your case. In the absence of any aggravating circumstances I do not envisage that they will bother trying to turn that into a “at the time of driving” positive result. It would cost them about £300 to get the back calculation done and the outcome would be probably inconclusive enough to justify trying for a conviction.
As to the timescale, they have 6 months to institute proceedings and then another few weeks to serve the summons on you, so you would have to sweat for 7 1/2 to 8 months before you could be sure you are in the clear. Hopefully the police will get back to you in 8 weeks or so, confirm the result and that they are taking no further action but as I said before, if they do ask you to go for an interview get legal advice at the police station an be guided by the duty solicitor on how to answer the questions.
 
Thank you, will keep you all updated as very little out there about actual back calculation cases. Think the lab may have already taken the 6 off, being a small, obese, diabetic woman would still anticipate no further action there had been no intention to drink drive, had been looking at some of the guidance and using falling blood alcohol level as 0.015 an hour I should of had a much lower bac, my own conclusion is that it's likely I drop 0.01 per hour which is the only sensible conclusion I can make, do you agree? Sorry for getting so technical, have an analytical job, thanks again
 
hi, I'm now coming up to 7 months since this happened, have not had any contact with the police, no interview, but also have not contacted them, can I now stop worrying about having a BAC calculation? Summons etc ?? Just still feeling in limbo
 
It’s 6 moths for them to process the summons etc so long as they they have started the process by 6 months then they have time to send you a summons but with all the back log that could be the delay - sadly I think you have longer to wait
 
7 months would be the top end of when a summons could be served, allowing for the maximum 6 months to raise on with the court.
as you were not interviewed for personal details to enable a back calculation I think you can be sure that you are in the clear.

Just remember the stress of the past 7 months next time you are tempted to have a couple of drinks before you drive!
 
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