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Blood Sample Analysis: .15%….But Was It Yours?


Let me tell you about one of my law firm’s DUI cases that ended up in a Los Angeles Times article entitled “DUI Case Botched by Blood Mixup”.

One of the attorneys in the firm had a young client who had been arrested for drunk driving by the Los Angeles Police Department and had a blood sample drawn from his arm. He swore to us that he was innocent, and we believed him. Problem: the blood alcohol content of the sample was .15% — almost twice the drunk driving limit.

Now what?

We obtained a portion of the sample from the LAPD crime lab and sent it to a private lab that we use for reanalyzing the blood samples of all our DUI clients. The lab reported the blood alcohol level to be .13% — lower than the police analyss, but still a long way from being under .08%. As we requested, they also tested for preservative and anticoagulent (either fermentation or coagulation can raise the alcohol level in the sample), but everything appeared to be in order.

Our client still insisted he was not driving under the influence of alcohol. The only other reasonable possibility was a faulty chain of custody. In other words, the LAPD lab got the vial  of our client’s blood mixed up and tested someone else’s blood. Kind of like the work they did in the O.J. Simpson case.

So we had the sample blood-typed to see if it was that of another arrestee. Result: type “O”– the same as our client’s. But, then, that’s the most common type of blood.

We decided to try something different, something that, to our knowledge, had not been done before in a DUI case. We had blood taken from our client and, with a portion of the remaining sample from the LAPD lab, shipped to an independent laboratory in Oklahoma that specialized in DNA testing.

A month or so later the report came back: the blood tested by LAPD was conclusively not that of our client.

The prosecutor in the case initially refused to accept these results. But after we proved that the comparison blood had come from our client and after LAPD checked the blood themselves, he reluctantly dismissed all criminal charges.  Predictably, in the L.A. Times article LAPD tried to point the finger at someone else:

Police officials said they are investigating how the mix-up occurred and who is responsible,  But, they said, they are fairly confident that the lab did not make a mistake.  One possible explanation, they said, was that the blood was mistakenly labeled when it was initially drawn by nurses at LAPD’s jail intake facility in Van Nuys. 

Typically, the police claimed infallibility: “We do not make mistakes…It was the nurses”. 

So how could this have happened? The truth is that it probably happens far more commonly than we suppose.

When a blood sample is drawn from the suspect in a DUI case rather than using a breath machine, the sample is supposed to be inserted into a vial containing preservative and anticoagulent, then shaken and sealed. Procedures require that a chain of custody be established: the location of the vial of blood must be identifiable at all times so that it does not become contaminated or mixed up with someone else’s vial. This is done by labelling the seal with identifying information, then usually placing the sealed vial in an evidence locker (which should be refrigerated but often is not) until it is transported to the crime laboratory for further storage and refrigeration. At any stage of this chain of custody, of course, things can go wrong with the vial or the records.

It may be a week or so before the vial is finally analyzed. This is commonly done using gas chromatograph instruments, and the vial is one of many analyzed in large “batches”. A batch is a group of vials, perhaps 40 or more, which are analyzed in sequence; this is much faster and more economical than isolating, identifying and separately analyzing one vial after another. Of course, it is critically important that the sequence of tests by the gas chromatograph coincide with the sequence of vials in the records. If the sequence of numbering of the vials is off by one, then the records will show a result from the analysis of another vial. And it won’t be just one person whose blood is falsely reported: every other vial will also be one off — and will all be wrong.  And you have 40 people people facing criminal charges based upon false evidence.

“How do I know the blood they tested was mine?” Simple – if you can get a portion of the sample from the crime lab and have an extra $1200 for DNA testing laying around. 

Otherwise, I guess you’ll never know….

The post Blood Sample Analysis: .15%….But Was It Yours? appeared first on Law Offices of Taylor and Taylor - DUI Central.

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