When someone is arrested for DUI, it is natural to look at the police report or chemical test result and assume the case is already decided. A reported BAC can appear very precise. An officer may describe several signs of impairment. The report may say that field sobriety tests were performed and that the driver did poorly.

But a DUI case is made up of many separate pieces of evidence. Each piece should be examined on its own and then compared with the rest of the evidence. A problem with one part of the investigation does not automatically mean the case will be dismissed. It can, however, raise questions about the reliability, admissibility, or strength of the prosecution's evidence.

In my experience defending people accused of DUI in Sacramento and throughout Northern California, the details can make a significant difference. Sometimes an important problem is not visible until the defense obtains the video, testing records, laboratory records, or other evidence that was not included in the initial police report.

What Is an Evidence Problem in a California DUI Case?

An evidence problem does not necessarily mean that evidence will automatically be excluded from court. That distinction is important.

Evidence may have problems involving the way it was obtained, documented, collected, preserved, tested, interpreted, or presented. Depending on the circumstances, a defense attorney may be able to challenge how evidence was obtained, question whether proper procedures were followed, dispute its reliability, or argue that the prosecution has not established the facts necessary to rely on it.

1. Questions About Why the Traffic Stop Happened

One of the first questions in a DUI investigation should be: Why did the officer stop the vehicle?

The reason for the traffic stop can become important because the legality of the initial detention may affect what happened afterward. If the officer's description of the driving does not match available video or other evidence, that difference deserves attention.

Dash-camera footage can be particularly useful. It can show what actually happened before the stop instead of relying entirely on a written description prepared after the fact.

This does not mean every disagreement between a police report and a video will result in dismissal. It does show why the actual evidence should be examined instead of simply accepting the description in the report.

2. The Police Report Contains Inconsistencies or Important Omissions

A police report is an important part of a DUI case, but it should not be treated as an unquestionable account of everything that happened.

A defense review may compare the officer's statements with dash-camera footage, body-camera footage, witness statements, photographs, dispatch records, chemical testing records, and other available evidence.

Questions may include:

• Does the available video support the officer's description of the driving?
• Are the officer's observations consistent throughout the report?
• Are important times documented accurately?
• Are there unexplained gaps in the investigation?
• Do witness accounts agree with the police report?
• Does the physical evidence support what the report says happened?

One inconsistency may not decide a case. But significant inconsistencies can become important when the prosecution depends heavily on an officer's observations.

3. Problems With Field Sobriety Tests

Field sobriety tests are frequently discussed in DUI reports. But the results are based on observations of a person's performance under particular circumstances. They are not a simple machine-generated measurement of intoxication.

The circumstances surrounding the tests can matter. An attorney may examine the instructions that were given, the way the tests were demonstrated, the surface where the tests were performed, lighting and weather conditions, footwear, physical limitations, and whether the officer accurately described the person's performance.

Medical conditions, injuries, balance problems, age, fatigue, nervousness, and other circumstances may also be relevant when evaluating what an officer observed.

A person performing poorly on a field sobriety test does not, by itself, establish every element of a DUI charge. The surrounding circumstances have to be considered.

4. Problems With a Breath Test

Breath testing can provide important evidence in a California DUI case. But a breath result comes from a testing process, and that process can be examined.

California's DUI rules address procedures involving forensic alcohol breath testing, including requirements concerning testing procedures, instrument accuracy, operator qualifications, and the collection of breath samples.

That means the investigation should not necessarily stop when the defense sees a BAC number on a report.

Depending on the circumstances, an attorney may examine:

• Whether the required testing procedures were followed.
• Whether the required observation period was properly completed.
• Whether the instrument was properly maintained and checked for accuracy.
• Whether the operator was properly trained.
• Whether the required breath samples were obtained.
• Whether the available testing records support the reported result.

A procedural issue does not automatically make a breath result inadmissible. The significance of the issue depends on the specific facts and applicable law.

5. Problems With a DUI Blood Sample

A blood test may appear especially convincing because a laboratory analyzes an actual biological sample. But the final BAC number is only one part of the evidence.

California regulations establish requirements concerning the collection and handling of forensic alcohol blood samples. The defense may therefore examine how the sample was collected, identified, preserved, stored, transported, and analyzed.

Blood Collection

The circumstances of the blood draw can matter. The person who collected the sample, the collection procedure, the materials used, and the condition of the sample may all be relevant.

California's regulations contain specific requirements concerning the cleaning of the collection site. For example, alcohol or another volatile organic disinfectant should not be used to clean the skin at the site where the blood is collected for forensic alcohol analysis.

Preservation and Storage

Blood samples must also be properly preserved and handled. A defense review may examine whether the appropriate preservative and anticoagulant were used, whether the sample was properly identified, whether it was stored appropriately, and whether the chain of custody is adequately documented.

Laboratory Analysis

The laboratory process may also deserve examination. Depending on the case, the defense may review laboratory records, analytical methods, quality-control information, instrument documentation, and other records associated with the reported BAC.

A blood result should therefore be evaluated as part of the entire testing process rather than treated as an isolated number.

6. The Chemical Test Was Performed After the Driving

Timing can be an important issue in a California DUI case.

The time of driving and the time of a breath or blood test are often different. Alcohol concentration can change over time, which is why the timeline surrounding drinking, driving, the traffic stop, arrest, and chemical testing may need to be examined carefully.

California Vehicle Code section 23152(b) provides a rebuttable presumption concerning a BAC of 0.08 percent or more when a qualifying chemical test is performed within three hours after driving. The precise legal significance of a test depends on the circumstances and applicable law.

7. The Evidence Does Not Match the Timeline

Building a DUI defense often begins with putting the events in chronological order.

When did the person leave? When did the alleged driving occur? When did the officer observe the vehicle? When was the vehicle stopped? When did the officer first speak with the driver? When were field sobriety tests performed? When was the arrest made? When was the breath or blood sample collected?

When the different records are compared, gaps or inconsistencies may become apparent.

For example, a chemical test performed after the driving may require the defense to examine the complete timeline and the circumstances surrounding the test rather than simply treating the later BAC number as a direct measurement of the person's BAC at the exact moment of driving.

8. Missing or Unavailable Video Evidence

Many DUI investigations can involve dash-camera footage, body-camera footage, surveillance video, jail video, or other recordings.

Video can sometimes provide information that is not contained in a written police report. It may show the actual driving, the traffic stop, the interaction between the officer and driver, or the administration of field sobriety tests.

A careful defense investigation should determine what recordings exist, whether they were preserved, and whether the recordings support or contradict the written account of what happened.

This is one reason I believe it is important to obtain the available evidence instead of relying only on the initial police report.

9. Witness Accounts Do Not Match the Police Report

Police officers are important witnesses in DUI cases, but they may not be the only people who observed what happened.

Passengers, other drivers, employees at nearby businesses, friends, family members, and other witnesses may have observed portions of the events.

Their observations may provide information about the driving, the person's behavior before the stop, the traffic stop itself, or what happened afterward.

Witness evidence does not automatically overcome the prosecution's evidence. However, when independent accounts materially conflict with the police report, those differences should be investigated.

10. Chemical Testing Records Raise Questions

The BAC printed on a laboratory or testing report is only one part of the chemical evidence.

Depending on the type of test, a complete review may involve laboratory records, instrument records, accuracy documentation, calibration information, sample identification, chain-of-custody records, and other testing documents.

The purpose of reviewing these records is not to assume that a test was wrong. It is to determine whether the testing process supports the result that the prosecution wants to use.

11. The Case Depends Heavily on One Piece of Evidence

Some DUI cases appear strong because one piece of evidence receives most of the attention.

It may be a BAC result. It may be the officer's description of the driving. It may be a statement allegedly made by the driver. It may be the officer's interpretation of field sobriety tests.

A careful defense review asks whether the other evidence independently supports that conclusion.

If a critical piece of evidence has a significant weakness, the defense may need to reconsider the overall strength of the prosecution's case. That does not guarantee a particular outcome, but it can affect how the case should be defended.

What Should You Do If You Think There Is an Evidence Problem?

The first step is not to assume that a potential problem automatically means the DUI case will be dismissed. The better approach is to have the available evidence reviewed carefully and systematically.

That review may include:

• The traffic stop and the reason the officer stopped the vehicle.
• Officer observations before, during, and after the stop.
• Field sobriety testing and the circumstances in which it was performed.
• Breath testing and the records associated with the instrument and testing procedure.
• Blood testing and the collection, preservation, storage, and laboratory analysis of the sample.
• Video evidence from police vehicles, body cameras, businesses, or other sources.
• Witness statements that may confirm or contradict the police account.
• The complete timeline from drinking and driving through the chemical test.

Why the Details of a DUI Investigation Matter

A DUI case can look very different after all of the evidence has been collected and examined.

A police report may tell one story. A dash-camera recording may show something different. A BAC result may appear definitive, but the records behind the testing may raise questions that need to be answered.

That is why I do not believe a DUI defense should be based solely on the face of the police report or the number printed on a chemical test.

The investigation needs to go deeper. The defense should determine what happened, how the evidence was obtained, whether required procedures were followed, and whether the evidence actually supports the conclusions being drawn from it.

I have been representing people accused of drunk driving since I began practicing in 1995. I have handled DUI jury trials, pretrial motions, and DMV hearings, and I continue to focus my practice on DUI defense.

You can learn more about my background through the John Campanella attorney profile .

Contact the Law Office of John Campanella

If you have been arrested for DUI in Sacramento or elsewhere in Northern California and believe there may be problems with the evidence, the case should be evaluated based on the actual records and circumstances.

You can use the Contact Info page to get in touch with the office.

Final Thoughts

A DUI arrest does not mean that every piece of evidence against you is automatically accurate or beyond question.

The traffic stop, officer observations, field sobriety tests, breath testing, blood testing, laboratory procedures, timing, video evidence, and witness statements can all deserve careful examination.

Do not judge the strength of a California DUI case solely by looking at the BAC number or the first page of the police report. The details behind the evidence can matter.

If there are inconsistencies, testing concerns, procedural issues, or potential constitutional problems, those issues should be identified and evaluated by an attorney familiar with California DUI defense.