Home > Blog > DUI Defense: Attacking the breath test in Los Angeles DUI Prosecution

DUI Defense: Attacking the breath test in Los Angeles DUI Prosecution

November 24, 2015

Many police officers consider all traffic stops a DUI investigation. Thus, the second you are stopped in Los Anglees by a police officer, you are suspected of a DUI! This is more so after accidents in Los Angeles, Orange County etc. For example, if you are stopped for not wearing a seatbelt, many police officers, CHP officers, or any other law enforcement officer, will note if you can be under the influence of alcohol or drugs. They are trained to detect any signs of alcohol consumption, such as open bottles, smell of alcohol and any other signs, such as red eyes and slurred speech. Drunk driving attorneys in Los Angeles specialize in defending people who are pulled over without a good reason. Los Angeles DUI attorneys will fight these cases by filing motions to suppress evidence. But even if police can come up with a good reason for the stop, Los Angeles DUI attorney can fight your case at trial by trying to show that DUI breath test was not accurate.

To prosecute a DUI in Los Angeles, the prosecutor needs to show impairment at the time of driving. Because tests of alcohol are measured much after the stop, the prosecutor have to present evidence of the BAC level at the time of driving. This is done through a formula crated in 1920th by a Swedish professor Erik Windmark. The formula is BAC = 100*A/(r* W) – B*t.

A = mass of alcohol consumed ( a drink is assumed to contain 10-14 grams of ETOH)

r = ratio of body water to alcohol and is assumed .68 for men and .55 for women.

W = body weight

b = rate of alcohol methabolism and is assumed to be .017 per hour.

t = time alcohol present in the body.

EXAMPLE: To calcluate his BAC at the time of driving we need to know, how much alcohol was consumed, what time the person started to drink, if it a male or female and how much that person weighs. The BAC levels for 120 lb female will be much different then for 200 lb male. Lets assume, this person is drinks 2 drinks (.02 kg), is a female (.55), who weight 120 lb (54 kg), and consumed alchol two hours before stop (.017 x 2). Then the BAC level at the time of driving will be estimated to be 100*.02/.55*54 – .017 *2 = .067-.034 = .033 BAC.

Los Angles DUI prosecutors usually use Windmark’s formula in a different way. Instead of determining the level of alcohol at a certain time, they modify the formual by solving it for number of drinks consumed. Typically, during a trial, Los Angeles DUI prosecutor asks his toxicology expert if he is able to determine a number of drinks a person had based on the level of alcohol presented. This can be easily calculated using Windmark’s formula by pluggin in the weight, gender, time after driving. The modified formual woud then turn into A = (BAC+B*t) * (r* W)/100

For example, if a hypotetical 175 lb male is .10 % BAC 1 hour after driving, Los Angeles DUI prosecutor asks his expert to use Windmark formual to estimate the number of drinks in that person’s body. The BAC, 1 hour prior to test (at the time of driving) would be .117 % BAC. Next Windmark must adjust for body weight and ratio of water to weight (79kg and .68 for man), to wit 53.72 and multiply by this number to get to 6 drinks.

If you were arrested for a DUI in Los Angeles, you were asked to give a sample of your blood or breath. If you agreed to provide a breath sample, you were probably taken to a police station where you blew into a machine to measure your blood alcohol level. There are several machined used by different police agencies in Los Angeles county. These machines sometimes use infrared light or sometimes use a fuel cell technology (making electricity) to measure amount of alcohol in person’s breath.

The breath machines are not accurate and have a margin of error that can be as high as .02% in some DUI breath test. That means that a .08% blood alcohol level can lower by .02%, and equal to.06% because the alcohol testing machines are very inaccurate. The prosecutor can argue that your blood alcohol level can be higher by .02%, but all evidence that can helpful or hurtful to you, must be used to help you. Armed with law and science, best DUI attorney Los Angeles can make sure you can fight your case in court.

Attorneys in our office can show to the jury that breath alcohol machines can give wrong results on your DUI breath test and have a .08% BAC in your breath is not true level of alcohol in your blood.