Houston DWI Attorney - Cross Examining Expert Witnesses on Blood Tests

Houston DWI Attorney - Cross Examining Expert Witnesses on Blood Tests.

Most DWI cases involve blood testing since the widespread use of Blood Search Warrants. If your case is headed to a trial your attorney needs to know how to cross examine a blood expert witness for the State. There are three main types of blood expert witnesses. 1. Police Officers, 2. Nurses/Phlebotomists, and 3. Forensic Scientists. We call forensic scientists who do DWI blood analysis "Blood Analysts."

1. POLICE OFFICERS

Cross Examining a police officer may not seem like an expert witness cross but it certainly should be in the context of DWI. First a Police officer should have to be qualified as an expert witnesses by the State in order to testify on the eye test called the Horizontal Gaze Nystagmus. Then the Police officer is often the source of information that is used to admit the blood result into evidence. The Police officer is probably the person who wrote on the collection documents affixed to the blood vials and is the one who observed the collection procedure.

1. Blood Draw Procedures - The police officer will not be intimately familiar with blood draw procedures even though he has probably seen it done many times. You can cross examine the police officer on things like whether a tourniquet was applied and if it should be applied.

2. Physical Symptoms of different alcohol levels - You can ask the officer if they are familiar with learned treatises like the Kurt M. Dubowki Chart on Stages of Acute Alcohol Influence. An officer who has been trained only in regular procedures for standardized field sobriety testing will be out of his league when discussing how alcohol concentrations can manifest themselves.

3. Blood vial integrity - An officer may know that a grey top forensic tube is used to take a blood sample in a DWI but he may not know that inside the tube there are preservatives and anti-coagulants that are supposed to be present or what their absence might mean for the integrity of the blood draw.

When you are cross examining an officer a helpful strategy is to "dejargon" what the police officer says. An officer might say, "I availed the defendant of the consequences of a possible refusal and administered the blood collection procedures." You mean, "You read him the form and brought him to the hospital to take his blood?"

Police will sometimes use fancier words than necessary to explain simple things and make it seem more like a scientific process than it really was. For example I administered the HGN test and saw distinct and sustained nystagmus at maximum deviation sounds good. But when you break it down for the jury and show that all that means is that the officer thinks his eye wiggled when he told him to look all the way to one side it shows the jury the simplicity of what the officer is saying he did or saw.

If you can get the jury to understand that the officer is just another person and is capable of making mistakes like anyone else they are more likely to accept that he can have credibility issues.

2. NURSES/PHLEBOTOMISTS

Nurses and Phlebotomists perform the same essential function in DWI cases. They are the ones that stick the needle in your arm to draw the blood. Phlebotomy means the surgical opening or puncture of a vein in order to withdraw blood or introduce a fluid, or (historically) as part of the procedure of letting blood.

There are two types of nurses or phlebotomists that we normally encounter. 1. Nurses employed at the hospital, and 2. Nurses or phlebotomists that have a contract with the police to draw blood.

1. Nurses Employed at the hospital are more likely to testify favorably to the defense because their income is not dependent in part by continued employment for DWI blood draws specifically. A nurse who's primary responsibility is the saving of lives will sometimes balk at the way blood is stored for weeks or months without being tested. Blood can sometimes turn green after months of storage and nurses who work primarily for hospitals will not find that to be an acceptable storage method. You can expose some of the poor practices of blood testing forensics by comparing it to the normal procedures of a hospital every day. For example, if a hospital wants to know an alcohol concentration for the purpose of saving the life of the patient they will test it immediately in the hospital lab while the blood is fresh from the draw. DPS may not receive the blood until it has been sitting in an evidence locker for more than a month.
   

2. Nurses or phlebotomists that have a contract with the police to draw blood. These nurses are doing multiple DWI draws for the police and can be cross examine on their connection to law enforcement as well as their financial incentive to testify on well on behalf of the state and lead to a conviction. Sometimes the best cross examination on a state contracted phlebotomist is no cross examination at all. If they followed their procedures properly (which they almost never do perfectly) then just say no questions. Don't step into it by asking if they felt the defendant was intoxicated, they'll say yes.

3. Forensic Scientists

The most formidable expert witness for the State in a DWI case is the forensic scientist from a police lab. You may encounter the Department of Public Safety, Houston Police Department, or Harris County Sheriff's Office Laboratory.

1. Obtain Blood Discovery - The first step in cross examining a lab analyst is obtaining blood discovery including copies of the data generated by the gas chromatograph. This will include service logs for each machine used by the lab analyst. The blood testing gas chromatograph that was used in your client's case may have gone out of service the week before or the week after your test. The maintenance logs of each instrument should be kept. It will also show you the results of the other blood draws that were in the same batch as your client.

2. Cross examine on bias and experience - If the lab analyst you have on your case is new then you may be able to cross examine them on their lack of experience. If they are a 15 year veteran of the DPS lab and have never worked for anyone but the government you may be able to cross examine that they have a bias towards the police in that they have been an expert in the field of blood testing for 15 years and have never testified for a defendant in that time.

3. Show how the process is not infallible - The Lab will typically keep the sample in a refrigerated temperature locker. However they will testify that no such refrigeration is necessary. "So your policy for your lab is to preserve the sample through refrigeration?" Yes. "But that policy is unnecessary?" Yes. DPS and other labs will try to make it seem like the process is infallible but no process really is. You can see where you can go from here. It is either better or necessary or not and the State shouldn't be able to have it both ways. Sometimes the best way to explain how strange this process is to a jury is to let them know that the defendant's blood was not tested on its own. It was likely tested with approximately 50 other samples. Ask the Lab analyst how many samples they have prepared and tested in their career and you're likely to get an answer like 50,000. Then ask in individually pipetting and recording by hand the samples how many times have you switched a sample by accident and they will tell you ZERO. It defies all logic and common sense to think that a human could perform any task 50,000 times with no mistakes.