Urine Testing in DUI Cases

Why and how urine testing for drugs and alcohol is used in DUI investigations and prosecutions.

All states have DUI implied consent laws that authorize the chemical testing of drivers to determine the presence and concentration of consumed alcohol or drugs. Under these laws, drivers who are lawfully arrested for a DUI offense must agree to test if asked to do so by an officer.

In most states, officers investigating DUI cases can ask the driver to take a blood, breath, or urine test. This article outlines the procedures for urinalysis in impaired driving investigations and some of the benefits and drawbacks with this type of testing.

How Consumed Drugs and Alcohol End Up in the Driver's Urine

In general, urine is produced by the body as a way to expel substances that the body doesn't need or can't process. Many impairing substances such as drugs and alcohol are, at least in part, expelled from the body in this way.

When consumed, drugs and alcohol pass through the liver and/or kidneys before finally being expelled from the body as urine. While alcohol is usually processed by the body within a matter of hours, certain controlled substances can reside in the body for weeks before being fully metabolized and expelled.

How Police Conduct DUI Urine Testing

Obtaining a urine sample is pretty straightforward with a willing participant. The person who's being tested just needs to provide the sample by urinating into a receptacle (cup).

Police can test a urine sample for drugs and alcohol either by using a chemical stick (sometimes called a "field test") or by sending the sample to a laboratory for quantitative analysis. While a field test can immediately tell police what substances the driver ingested, only lab testing can provide information about the quantity and concentration of the consumed substances present in the urine.

To prove a DUI charge in court, prosecutors generally need to prove the actual concentration of alcohol and drugs in the driver's system. So, police normally send urine samples to a lab for testing.

Benefits of Urine Testing in DUI Cases

The three types of tests police typically use in DUI investigations (blood, breath, and urine), all have certain advantages. The main benefits of urine tests are they provide police with immediate results (using a chemical stick) and can detect both drugs and alcohol.

In contrast, blood tests—though they're the most accurate of the three tests—don't provide any information about the drugs or alcohol in a driver's system until the sample is tested at a lab. And, although breath tests give instantaneous and fairly accurate results as to alcohol, they don't test for drugs.

For these reasons, urine tests are most commonly used by police when they suspect the driver is under the influence of drugs and—for some reason or another—blood testing isn't a viable option (for instance, some drivers have prohibitive medical conditions). Police might also test a urine sample with a chemical stick to get a preliminary idea of what the driver has in his or her system. If the test is positive for drugs, police can then request a blood sample, which will provide the most accurate measurements of the substances in the driver's system.

Limitations and Disadvantages of Urine Testing in DUI Cases

While it's one of the oldest methods of testing for drugs and alcohol, urine testing is quickly phasing out as a go-to investigative tool in DUI cases. Basically, police don't normally opt for urine testing because the disadvantages outweigh the benefits in most cases.

Problems Obtaining a Urine Sample from the Suspect

Many of the drawbacks with urine testing stem from the difficulties officers face in obtaining an adequate sample. Urine testing requires a willing participant, and impaired suspects aren't always the most cooperative people. There's not much an officer can do if the suspect can't or won't provide the sample.

Observation can also be a problem. Someone needs to observe the suspect giving the urine sample to ensure its integrity. So, generally, there must be an observer available who's the same gender as the suspect, which isn't always the case. And many suspects don't want someone watching them urinate regardless of the gender issue. It's not uncommon for a driver to claim they can't urinate under these circumstances or just outright refuse to comply.

Problems With the Accuracy of Urine Test Results

Urinalysis is generally considered the least reliable DUI testing method. The DUI laws in many states make it illegal to drive with a blood alcohol concentration (BAC) of .08% or more. But urine testing doesn't measure blood alcohol directly and the amount of alcohol in a driver's urine isn't the same as in a driver's blood.

So, to obtain BAC from a urine test, a conversion is necessary. Without going into the details, this conversion produces only a BAC estimate, which isn't always very accurate.

Defense attorneys can capitalize on this weakness and might be able to cast enough doubt on the results to beat a DUI charge in court.

Talk to a DUI Attorney About Your Case

If you've been charged with a DUI based on a failed urine test, consult with a qualified DUI attorney as soon as possible. An experienced local attorney can evaluate your case and determine whether you have any viable defenses.

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