The Expert will be specific knowledgeable people at the Department of Transport, Arrive Alive Communications, the Road Traffic Management Corporation or others who might have the expertise to answer the question.
It would be foolish to make any predictions regarding want the blood alcohol concentration would be in a particular sample after prolonged storage. With prolonged storage the alcohol concentration could have been higher, lower or the same as at the time that the blood was taken from the accused.
The concentration of alcohol obtained, should the blood sample not contain sodium fluoride, could be higher, lower or the same as the alcohol concentration at the time that the blood was sampled. Only by testing the blood sample for the presence of possible contaminants such as micro-organisms that consume alcohol (Serratia marcescens and Pseudomonad sp.) or produce alcohol in the presence of adequate glucose (Candida albicans and Saccharomyces cerevisiae), could the obtained value be interpreted correctly.
There is also a chance that no contamination took place, which might indicate that the alcohol concentration reported, might indeed be accurate. Also note that a low storage temperature can protect the sample, even if it had been contaminated and if it contains insufficient fluoride.
Alcohol loss due to oxidation could also occur over time, and with opening and closing of the tube due to evaporation.
The following references look at the efficiency of Sodium Fluoride as preservative, as well as at storage temperatures and prolonged storage of blood samples where blood alcohol analysis is required.
References
1. Lough, P.S. and Fehn, R., “Efficacy of 1% Sodium Fluoride as a Preservative in Urine Samples Containing Glucose and Candida albicans,” Journal of Forensic Sciences, 1993, 38(2): 266-271.
2. Amick, G.D., Habben, K.H., “Inhibition of ethanol production by Saccharomyces cerevisiae in human blood by sodium fluoride,” Journal of Forensic Sciences, 1997, 42(4): 690-692.
3. Dick, G.L. and Stone, H.M., “Alcohol loss arising from microbial contamination of drivers’ blood specimens,” Forensic Science International, 1987, 34: 17-27.
4. Harper, D.R., “A comparative study of the microbial contamination of post-mortem blood and vitreous humour samples taken for ethanol determination,” Forensic Science International, 1989, 43: 37-44.
