Drivers do not need to prove their innocence at trial. The prosecutor must prove each element of DUI beyond a reasonable doubt. If she fails, the court will dismiss the charge. If she proves the elements of DUI but fails to prove an enhancement, the judge will strike the enhancement, and convict for the DUI. A defense could be simply waiting for the prosecutor’s case to fail, or it could mean presenting witnesses and documents, having an independent toxicologist testify, challenging the police conduct, etc.

The defenses available and the best trial strategy change in every case. Most defenses are available whether the driver committed the offense or not. The defense can always use the procedural and evidentiary rules to its advantage, capitalize on mistakes from the prosecution, and try to show that the prosecution’s evidence is incomplete or unreliable.


Virginia Rules of Evidence

The rules of evidence determine what is admissible at the different stages of trial. Keeping a single important piece of evidence out of the trial can be enough to prevent the prosecutor from proving an element of the charge. To do that, the defense must object to the evidence when the prosecutor offers it. The court will not apply the rules on its own, and, like the prosecutor, may not even realize or understand that there is a problem until the objection comes.

There are many evidentiary rules, and they are complicated. Knowing them well is a huge advantage at trial. The rules that come up the most in DUI cases are:

  • Hearsay. There are more than twenty exceptions, but the hearsay rule prevents witnesses from testifying to statements made by others or the contents of documents. It can also keep documents out in some cases.
  • Authentication. Documents that satisfy the hearsay rule are not admissible without evidence of their validity.
  • Best evidence rule. This is another hurdle for using a document at trial. Some documents that satisfy the rules for hearsay and authentication are still inadmissible without a specific certification. Some testimony may also be inadmissible because a document exists about the matter.
  • Relevance. Only relevant evidence is admissible. Evidence is relevant if it changes the likelihood that something important occurred, like an element of the offense. Evidence can be relevant to one element, but irrelevant to others. When that happens, the defense can request a ruling that the evidence is only to be considered for a limited purpose.
  • Personal knowledge. A witness cannot testify to a fact unless she perceived it with her own senses. However, many witnesses testify as though their conclusions are facts they witnessed. Defense counsel can prevent this and make the court draw its own conclusions based on the facts presented. Catching this can change eye-witness testimony that would result in conviction to a circumstantial case.
  • The DUI statutes contain additional rules about evidence the prosecutor cannot use at trial, which are discussed in the substantive defenses section below.
  • There are many more rules that could come up in a DUI trial.


Procedural Defenses

These defenses apply when the police or prosecutor violate the rules of Virginia or Constitutional criminal procedure. They apply to all criminal charges.


Constitutional Criminal Procedure

Fourth Amendment

The Fourth Amendment protects against unreasonable searches and seizures by the police or other government actors. The police must have good reason to detain someone, and they cannot keep someone detained without. Once that reason goes away, the police must let the person know he/she is free to leave. Traffic stops, activating emergency lights, and DUI roadblocks or sobriety checkpoints are examples of detentions.

Arrests require probable cause to believe the person has committed a crime. Searches require probable cause to believe that the search will uncover evidence of a crime. The police must obtain a search warrant before searching someone unless they search in the process of arrest

Unlawful detentions, arrests, and searches occur regularly. In most DUI cases, a successful fourth Amendment challenge based on an unlawful detention or arrest means the prosecutor cannot proceed and the court dismisses the case. For unlawful searches, the court usually suppresses any evidence the police obtained from the search, even evidence obtained indirectly. This could change the outcome of a DUI trial, and often leads to dismissal of whatever charges resulted from the search, such as possession of drugs, concealed weapons, or other contraband.

Fifth Amendment

The Fifth Amendment protects against self-incrimination. The police must inform anyone in custody, which does not require an arrest, of the right to remain silent, to have an attorney present during questioning, and to have an attorney appointed if the person cannot afford one. These are called the Miranda rights. When the court finds that the police violated the Mirandarights, it may suppress statements made after the violation, and any evidence the police discovered because of the statements.

Sixth Amendment

The most important Sixth Amendment rights in DUI cases are the right to confront witnesses at trial and the right to counsel for the material stages of a case. They affect the admissibility of certificates of analysis for blood and breath testing, and prior convictions for DUI or related offenses in enhanced DUI cases. The substantive defenses section discusses both contexts below. Other Sixth Amendment rights that come up infrequently include:

  • Speedy, public, impartial jury trial
  • Notice of the charges
  • Right to process


Virginia Criminal Procedure

Defenses that could fit into this category are based on procedural rules found in the DUI statutes. Therefore, they are discussed in the next category. The defenses that follow are uncommon, but still important.

Statute of Limitations. This is a deadline for charging misdemeanor offenses. The Commonwealth must charge misdemeanor DUI, reckless driving, and other traffic offenses within one year of the offense, or it cannot prosecute them. The statute of limitations does not apply to felonies in Virginia.

Speedy trial. Besides the Sixth Amendment, Virginia has its own speedy trial rights that apply to felony offenses and appeals from misdemeanor convictions. For felonies the deadline is nine months from the preliminary hearing. For direct indictment cases, the clock starts when law enforcement serves the defendant with the indictment. If the defendant is incarcerated for the charges pending trial, the deadline is reduced to five months.

For misdemeanors, the deadline for trial in circuit court is nine from either the general district court conviction or service by law enforcement with a direct indictment. The deadline is five months if the defendant is in custody for the charges.

Double jeopardy statutes. Virginia provides slightly different protection from multiple prosecutions than the double jeopardy clause of the Fifth Amendment. The three most important to DUI and reckless driving cases:

  • Conviction for an offense prevents subsequent prosecution for any other offense based on the same conduct. For example, if the prosecutor learns during a DUI trial that the driver committed an unreported hit and run, it would be too late to prosecute it.
  • A DUI or “general” reckless driving conviction bars conviction for the other offense based on the same driving or operating. The rule applies even when both offenses are tried at the same time.
  • *Prosecutors cannot charge a more serious offense after successful appeal from a circuit court conviction.

Venue. The prosecutor must prove that the charges are pending in the court for the city or county, which is usually where the offense took place. Venue is not considered an element of a criminal offense, but the court must dismiss the charge if the prosecutor fails to prove it.

Defenses based on Virginia’s DUI laws

These defenses are based on the elements of DUI or the enhancements. Defendants can present evidence of innocence on any of the elements. However, the court will dismiss the charge if the prosecutor does not prove the case, even with no evidence from the defense. Many cases are won simply by challenging the evidence and requiring the prosecutor to prove what happened.

Driver Impairment

In cases involving alcohol, cocaine, PCP, methamphetamine, and MDMA, blood test or breathalyzer results may be enough for a conviction with no other evidence of impairment. In other DUI cases, the blood test result may be the only evidence that the driver even consumed drugs. Sometimes it is possible to keep the test results out of evidence or discredit the result. Success does not guarantee that the court will dismiss the charge, but it means the prosecutor must prove impairment with other evidence.

Keeping the blood or breath test results out of evidence.

Some reasons for inadmissibility include:

  • Improper notice to the defense that the prosecutor intends to use the certificate of analysis at trial.
  • Errors in the certificate of analysis.
  • Insufficient evidence that the offense triggered the implied consent law requiring the driver to provide a blood or breath sample. For the implied consent law to apply:
    • The offense must occur on a highway. Highways include public roads and some private property.
    • The arrest within three hours of the offense. This comes up mostly in cases involving accidents or other situations when the investigation takes longer than a typical traffic stop. Also, sometimes police officers do not document the time of arrest and/or the time of the offense and forget by the time of the trial.
  • Blood test given instead of breathalyzer. In alcohol cases, the police must request a breath sample from the driver when the breathalyzer is available. Blood test results are only admissible if the breathalyzer is unavailable, or the police have good reason to suspect that the driver has consumed drugs.
    • * If the police do not offer a blood test, when medical issues prevent the defendant from providing a valid breath sample, the court must dismiss the DUI charge (and the refusal that the officer often charges at the same time).
  • Noncompliance with breath/blood testing procedures. The procedures are complicated. Some errors render the test result inadmissible. Others may detract from the result’s reliability. Types of issues that come up:
    • Malfunctioning or improperly maintained equipment
    • Breathalyzer operator error, including pre-test procedures
    • Improper blood draw or testing procedures
    • Mistakes or omissions in the documentation
  • Insufficient evidence that the drugs found in the defendant’s blood could have caused the type of impairment seen in the case. This applies to prosecutions under conditions (ii) and (iii) where there is no presumption of impairment.


Discrediting the test results.

When the blood or breath test results are admissible, they may not be reliable. Reasons the result may be inaccurate include:

  • BAC or drug levels rising after the offense. Absorption of alcohol and drugs occurs over time. From the time of arrest until the time of the blood or breath test, the driver’s BAC or drug levels will rise or fall depending on the time of consumption and the rate of absorption. Many factors affect the rate of absorption, including body weight and composition, metabolism, age, and sex, among others. When there is reason to believe the BAC or drug levels rose after the arrest, the test result may not be enough to prove impairment.
  • Lower results from independent blood test. The defense can have the blood sample independently analyzed. A lower result from a credible laboratory may indicate a problem with the test the prosecutor relies on.
  • Procedural errors in the testing process. As discussed above, procedural errors in blood and breath testing are common. Errors that do not render the certificate of analysis inadmissible may diminish its credibility.
  • The driver has certain medical conditions like diabetes or GERD which can affect test results.
  • Drug/alcohol consumption between the time of the offense and the blood or breath test.
  • Likelihood of driver impairment is difficult to determine without information about the driver. Drugs and alcohol affect everyone differently. At various levels, one person might be impaired while others are not. Therefore, blood or breath test results alone may not go far towards proving impairment except when the results exceed the statutory limits. For example, a driver who is weaving badly could be impaired, but could also be distracted by her phone or something else. The prosecutor is responsible for proving what happened.

When the test result is inadmissible or unreliable the prosecutor must prove driver impairment in some other way or the court will dismiss the DUI. The prosecutor can never use the following as evidence of impairment:

  • Preliminary Breath Test results
  • Prior convictions for DUI or any other offense
  • Refusal to provide a blood or breath sample
  • Testimony that someone was drunk, intoxicated or impaired; witnesses can testify about facts that they observe but not to the conclusions they draw from those facts

Prosecutors look at the defendant’s driving prior to arrest, performance on the Standardized Field Sobriety Tests (SFSTs), physical appearance (bloodshot eyes, slurred speech, loss of balance etc.), and any incriminating statements the driver may have made. This evidence helps the defense more than the prosecutor in some cases, but even bad evidence may often be explained. Medical conditions, fatigue, distraction, or problems with the vehicle could explain poor driving performance. The better the driving, the more difficult it becomes for the prosecutor to prove impairment.

There are several ways to counter the SFSTs. Medical, mental health, or physical conditions, age, fatigue, and distraction can all explain poor performance. Also, many officers administer the tests improperly, and they are never administered they are never administered under conditions like those of the studies that validated them. Sometimes the judges disregard the FSTs altogether when the police officer’s testimony is bad enough.

Driving or Operating

Although most conduct when the keys are in the ignition is “operation” under the DUI statute, prosecutors sometimes have trouble proving what happened or who the driver was if there is no eyewitness to the driving at trial. Circumstantial evidence can prove the element, but it must do so beyond a reasonable doubt. Strong suspicion is not enough.

Motor vehicle

The definition of “motor vehicle” is very broad. The rare cases where this element is an issue usually involve nonstandard vehicles i.e. not a car, truck, or motorcycle. Because the definitions from the Virginia Code are very specific, if the officer does not document her observations about the vehicle, she may not be able to prove what it was.


Getting rid of these eliminates the extra fines and mandatory jail time.

Subsequent offenses. Felony DUIs and second-offense misdemeanors require the prosecutor to prove that the defendant has a prior conviction. They usually use copies of the conviction orders for the prior offense. However, the orders often contain incomplete, inaccurate, or conflicting information. Some defects include whether:

  • the conviction complied with the defendant’s 6th Amendment right to counsel
  • the conviction order adequately identifies the defendant and the offense
  • out of state convictions are based on DUI statutes that are similar enough to the Virginia DUI statute
  • the prior offense occurred within the appropriate date range
  • the order is complete and properly certified

Incomplete or defective orders may be inadmissible or may not provide the proof necessary for the enhancement.

Elevated BAC. As discussed in the impairment section, problems with the blood or breath test may discredit the result or prevent its admission altogether. The same issues apply to the enhancement for elevated BAC. In addition, only blood tests conducted on “whole blood” can prove elevated BAC. Hospital bloodwork is usually on serum rather than whole blood. Several situations are possible:

  • The court denies admission of the test altogether leaving the prosecutor with no way to prove elevated BAC.
  • The court allows the test into evidence, but the test is not reliable enough to prove the enhancement.
  • The court admits a test on blood serum into evidence to prove impairment, but not to prove the enhancement.

In these situations, the court may still convict for the DUI if there is enough other evidence of impairment.