Confused by the 6mg deduction in blood tests

[rpc30]

Good evening, i'm hoping somebody may be able to assist me with some clarification.

Following a marginal breath test failure I opted for a blood test. I sent the sample given to me away for independent analysis. The sample was returned with a certificate showing the my blood alcohol level was 83mg. 3mg over the legal limit.
I have read on numerous occasions that the reading will have 6mg deducted from the final result so as to allow for a margin of error. My confusion lies with whether the results i have been sent will have already had the 6mg deducted from them, or whether this is done later by the police/cps?
The uncertainty is from the fact that i have read that the 6mg is deducted before the final result, if the blood test is carried out on behalf of the police. As this wasn't for the police, will the 6mg have been deducted?

I hope someone will be able to give me some guidance.

Thank you very much in advance.

 

[SeanJoyceStephensons]

The deduction is either 6mg or 6%, whichever is the greater.

You will need to ask the forensic labororatory that analysed your sample for confirmation of whether they have made the deduction or not. Only they know for sure.

 

[rpc30]

Thank you for replying and confirming the 6mg/6% issue, I really am very grateful.
I also think it's very decent of you to offer free advice like this, so thanks again.
I shall call the lab tomorrow.
All the best.

 

[SeanJoyceStephensons]

You are very welcome.
The other key indicator is that when the deduction has been made the certificate of analysis usually says " an alcohol content of not less than ...mg". Check what it says as this usually gives it away.

 

[rpc30]

Again, thank you for that.

The certificate i have says: For the purpose of section 16 road traffic offenders act 1988. It then lists all my details and the Polices details etc before going on to say: Method TOX16. alcohol in Blood 83mg/100ml. The expanded uncertainty of measurement at the 80mg/100ml level is +/- 1mg/100ml and is based on a coverage factor of 2 providing a confidence of approximately 95%.

Nowhere does it say 'not less than' but does the 'expanded uncertainty/coverage factor 2' part mean that it has had it deducted or it's still to be deducted? Particularly as it clearly says it is not 100% accurate but only 95%. They don't make this easy do they?

Thanks again for your input.