The Deregulation Act 2015, passed at the fag end of the last Parliament, has repealed the previous law which allowed someone over the drink drive limit but who had breathed less than 50mg to ask for blood or urine to be taken instead. The amending section can be found here:
http://www.legislation.gov.uk/ukpga/2015/20/schedule/11/enacted
This is unfair on the vast majority of motorists. All lawyers know that there can be some quite dramatic variations in the readings given on the machines. Someone who has breathed under 50 (and in particular under 40) should not be convicted by a machine with a tolerance that suggests that with another breath the reading may have been under 35. This section wasn’t a “loophole” in the original Road Traffic Act but an important safeguard in stopping a driver being unjustly convicted by machinery which by its very nature can never be one hundred percent accurate (but where the presumption is that the machinery is working properly in law). It is not the fault of drivers that it takes a long time, on occasion, for a doctor to come and take a blood sample by which time the blood / alcohol level will be below the limit. The fact that forensic medical examiners may be dealing with other prisoners or be too overworked shouldn’t lead to unmeritorious convictions. This isn’t a “deregulation” law which any government supposedly on the side of individual liberty should be proud of. Rather, it is a law which shows us sleepwalking into an inquisitorial justice system where the citizens’ rights are rendered nugatory. The interests of expediency and saving a buck trump everything.