The police are required to retain a portion of the blood or urine sample. The defendant and his/her defense attorney can then request that the prosecutor hand over that sample and conduct a test on it at an independent laboratory. The results of the independent test sometimes show that:
- The defendant's blood alcohol concentration (BAC) was actually lower than the prosecution claims, or
- The police did not abide by Title 17's regulations in their handling of the blood or urine sample.
But what if the results of an independent blood test following a blood split motion don't show anything beneficial to the defendant? What if the results actually work against the defendant (for example, if the test shows that his/her BAC was actually higher than the prosecution claims)?
In this situation, the blood split won't help you. But it doesn't have to hurt you either. As a DUI defendant in California, you are not required to disclose to the prosecution any evidence that you don't plan to introduce at trial. So if the test results from your blood split are not helpful to your case, nobody needs to know about them except you and your DUI defense attorney.
And it's worth noting that even if the blood split re-test shows that your BAC was as high as the prosecutor claims it was, that doesn't mean the test can't still be helpful to your defense.
It might reveal that the blood sample was contaminated or wasn't sufficiently mixed with preservative or anticoagulant, for example. If this is the case, you can challenge the admission of the prosecutor's DUI blood test as evidence against you.