8 Common Police Errors in DUI Cases


The police sometimes fail to follow specific procedures while doing driving under the influence (DUI) investigations. Requesting a motion to suppress incriminating evidence can be done if proven that the officers truly made mistakes. Listed here are eight of the most common police mistakes that can significantly influence the outcome of a case.

1. Conducting Investigative Stop with Insufficient Reasonable Suspicion

There are many instances when police officers hold insufficient reasons for stopping you over. The law states that before an investigative stop, police officers should tell you why you are asked to pull over and must have any of the following reasons:

  • Overspeeding;
  • Unlawful or unsafe changed lanes;
  • Failure to make a full stop at a stop sign;
  • Weaving in traffic lanes;
  • Napping or sleeping on the road; and
  • Engagement in any unsafe conduct or vehicle code infraction/violation.

If the police officers mentioned that they based their suspicions on their instincts and hunches, it would lead to the exclusion of all evidence obtained due to the illegal stop. Hence, you should not allow police to stop you when they have groundless suspicions. Law enforcement officers can only ask you to pull over with no reasonable doubt at a checkpoint.

2. Not Obtaining Drinking Patterns

Not only police officers but prosecutors sometimes err on making testimonies showing the drinking pattern of an alleged DUI driver. These statements include how many drinks a person had, and the time he or she had his or her last drink, which would affirm that a person’s BAC was at an illegal level when he or she is driving.

The law states that the rebuttable presumption of a DUI allegation is when a person has 0.08% BAC. Further, a prosecutor often relies on expert testimony from toxicologists who do chemical test many hours after the alleged time of driving, which most of the time leads to inaccuracy of a DUI claim.

3. Doing Field Sobriety Tests (FST) Incorrectly

The National Highway Traffic Safety Administration (NHTSA) provided three standardized field sobriety tests done after a DUI investigative stop. The police officers will ask you to do many instructions. If the officers give you incorrect instructions, then the test indicating your alleged impairment will be considered less reliable.

4. Not Following the 15-Minute Rule Close Observation before a Breath Test

The law requires a police officer to constantly observe an alleged DUI driver for 15 minutes before administering a breath test. Many officers routinely not follow this directive in different ways, as follows:

  • Transferring a suspected DUI driver to a police station before conducting a breath test;
  • Leaving the alleged driver alone while preparing to administer the test; and
  • Failing to note an entry about the time that the 15-minute observation started.

Your defense lawyers can argue that an officer’s failure in abiding the Title 17 directives may affect the breath test and cast reasonable doubts on the results. Contact Legal Aed DUI Lawyers for more of this.

5. Making Breathalyzer Test Errors

There are two common errors that police officers make when conducting breathalyzer tests. First is when they forget to obtain two breath samples. Another is when the operators categorized and submitted the two test samples incorrectly.

6. Incorrectly Admonishing Chemical Test Refusal

Most jurisdictions, like in California, specifically require officers to admonish the alleged DUI drivers of the possible consequences for not taking a chemical test after an investigative stop for a DUI.

There are situations when officers fail to admonish chemical test refusal properly. For instance, if the police officer did not read the admonishments as required by the law, you may be exempted from license suspension. Also, if an officer gave incorrect information about the time frame for license suspension, the length of suspension may be lowered.

7. Breaking the Chain of Custody in a Blood Draw

Blood samples for DUI with no proper foundation laid cannot be presented at a trial. Samples are handled by many people, who should all be recorded, including each of their respective times of custody. If the protocol is not followed and the chain of custody is interrupted, your attorney can move the court to exclude or suppress the sample from the trial.

8. Forcing Blood Draw with no Warrant

The police can now adequately obtain warrant electronically. Nevertheless, if officers force someone in producing a blood sample and restrain him or her against his or her will without a warrant, the test of the blood sample will be not acceptable at a trial.


There are some scenarios wherein the police are copying and pasting police reports. They might do this perhaps out of time constraints or laziness. Your lawyer can file a Pitchess Motion to determine whether your investigating officer is disciplined for such conduct.

Michael J Aed




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