Want to retest blood sample it's been 3 months since draw
A blood re-test may well produce a different result. I assume you have an attorney, if so he/she is in the best position to provide meaningful analysis and advice about your case. If you don't have an attorney, you should hire one ASAP. I offer a free consultation. Best of luck.
It could come back lower or the same or higher; you would generally want the latter, because that would show an arguable lack of sufficient preservative, meaning the first test some time after the driving was artificially high from fermentation. I do not believe in retesting, unless the client is so adamant that he had no alcohol in his system than we want to prove the sample tested was not his blood. But contrary to many of my colleagues in the field, I don't want retests so I can credibly object that the government slothfully did not test for preservative and hence the sample is forensically defective. If it comes out that I got a split for my own test, I can no longer credibly maintain that there is a question mark about preservative. Question marks equate to reasonable doubt, if the jurors are faithful to their duties. www.kennedyforlaw.com
In my experience, I generally see them drop no more than .01%, though on rare occasion I have seen more. They can also be higher as well if there is contamination or lack of preservative in the vial. So, if you are asking because you are wondering if it is worthwhile to see if it is actually lower, there are other reasons to test it, such as confirming whether there is sufficient preservative in the sample. There should be about 1-2% of a preservative called "sodium fluoride", or NAFl. You'll note it is similar to "sodium chloride" or NACl, which is common table salt. NAFl is a type of "salt", and like most salts, kill bacteria. When employed in a blood sample tube, the bacteria should be killed, which prevents those bacteria from converting blood sugar into ethanol ("alcohol"), and making it look like your alcohol levels were higher than they really were. So getting a split done has other advantages than just seeing if the results might drop a little. If it is much higher than when tested, there may be insufficient preservative and/or contamination which means that when it was originally tested by the crime lab, it was likely higher than the "true" levels at the time the sample was taken. This would provide a good defense strategy to question the validity of the test results.