20 Things the Crown Must Prove in an Impaired Driving Case

Impaired Driving What the Crown Attorney Must Appove

In an impaired driving or DUI charge, the Crown Attorney must prove every essential part of the case beyond a reasonable doubt.

If the evidence is weak, the police made mistakes, or your legal rights were violated, the Crown may not be able to meet that burden, causing the charges to be dismissed.

On this page, as impaired driving lawyers in Toronto we explain 20 important things the Crown must prove before someone can be convicted of impaired driving in Ontario. Understanding these issues will help you see why every case deserves a careful review by our seasoned and experienced dui lawyers.

If you have been charged with impaired driving, speak with Toronto DUI lawyer Nicholas Charitsis before making any decisions about your case. Nick is a former Crown Attorney with more than 25 years of experience defending impaired driving charges throughout Toronto and the GTA. Call 416-731-7113 for confidential legal advice.

1. Must Prove You Were Driving

Before you can be convicted of impaired driving, the Crown Attorney must prove the identity evidence. Who was driving, who is the person accused.

It may sound obvious, but someone has to come to court and identify you as the driver of the motor vehicle. As well the police officer must be able to identify the person they arrested in the court of law. As many times trials take months to come to court, this may become an issue.

The Crown may use evidence such as:

• Witness statements
• A driver’s admission
• Police observations
• Dashcam or surveillance video
• Cell phone or other electronic evidence
• Physical evidence from the scene

Problems can arise when:

• Police arrive after a collision.
• More than one person was in or near the vehicle.
• No one actually saw who was driving.
• Witnesses give conflicting accounts.
• Important evidence is missing or unreliable.

Related topics: If the allegation involves a parked vehicle rather than someone actively driving, you may also want to learn about Care and Control while Impaired charges, where the Crown must prove a different set of legal requirements.

2. Police Must Have Lawful Grounds to Stop Your Vehicle

Not every traffic stop is legal. In most cases, the police must have a lawful reason to stop your vehicle before investigating an impaired driving offence.

A traffic stop may be lawful if:

• You committed a traffic offence.
• Police were investigating a crime.
• Police were conducting a lawful roadside check.
• Police had another legal reason to stop your vehicle.

A stop may be challenged if:

• Police had no legal authority to stop you.
• The reason for the stop is unclear or inconsistent.
• The officer’s notes do not support the reason given.
• The evidence shows the stop was not lawful.

If the traffic stop was unlawful, it may affect the evidence the police collected afterward. In some cases, the court may exclude important evidence because your Charter rights were violated.

Related: Learn more about Charter rights in impaired driving cases and how an unlawful traffic stop can affect the prosecution.

3. Reasonable Suspicion to Demand a Roadside Breath Tests

Before the police can require you to provide a roadside breath sample, they must have a reasonable suspicion that you have alcohol in your body. A hunch is not enough. The judge will be looking for one of two items.

Police may rely on things such as:

• The smell of alcohol on your breath.
• An admission that you had something to drink.

The court will look at all of the circumstances to decide whether the officer had enough information to make a roadside breath demand.

If the officer did not have reasonable suspicion, the roadside breath demand may not have been lawful. Where the roadside breath demand is deemed unlawful, the results of that test will be deemed inadmissible, to which any charge being supported by breathalyzer readings will be dismissed.

Related: Learn more about roadside breath tests and the legal requirements police must meet before making a roadside demand.

4. Reasonable and Probable Grounds to Make Arrest

The police cannot arrest someone for impaired driving based on a suspicion or a hunch. Before making an arrest, they must have reasonable and probable grounds to believe that an impaired driving offence has been committed.

To decide whether those grounds existed, the court may consider:

• How you were driving.
• The smell of alcohol on your breath.
• Slurred speech.
• Bloodshot or watery eyes.
• Poor balance or coordination.
• An admission that you had been drinking or using drugs.
• The results of a roadside breath test, if one was taken.
• Other observations made by the police officer.

The court looks at all of the evidence, not just one observation. A single fact may not be enough to justify an arrest. Every case depends on its own facts.

If the police did not have reasonable and probable grounds to arrest you, the defence may argue that the arrest was unlawful. In some cases, that can affect whether important evidence is admitted at trial.

5. Where Proper Arrest Procedures Followed

Once the police decide to arrest someone for impaired driving, they must follow the proper legal procedure. These are important legal requirements, not just formalities.

The police must:

• Tell you that you are under arrest.
• Tell you why you are under arrest.
• Tell you that you have the right to speak with a lawyer.

These steps should also be recorded in the police officer’s notes and other disclosure provided to the defence. The Crown Attorney relies on this evidence to prove that the proper procedures were followed.

If the police fail to follow the proper arrest procedure, it may become an important issue at trial. A single mistake does not automatically mean the charge will be dismissed. However, one significant error—or several smaller problems taken together—may weaken the Crown’s case or affect the outcome of the trial.

That is why every part of the police investigation should be reviewed carefully.

6. Your Right to Speak With a Lawyer Was Respected

If you are arrested for impaired driving, the police must tell you that you have the right to speak with a lawyer without delay. This is one of the most important rights protected by the Canadian Charter of Rights and Freedoms.

The Crown Attorney will have to prove that:

• You were told that you had the right to speak with a lawyer.
• You were told about free legal advice, such as duty counsel, if it was available.
• Your rights were explained in a way that you could understand.
• You were given a reasonable opportunity to contact a lawyer.
• You were able to speak with your lawyer in private.
• The police did not continue questioning or investigating you before your right to counsel had been respected, unless the law allowed them to do so.

The police officer’s notes and the disclosure should show when your rights were read to you, what was said, and when you were given an opportunity to speak with a lawyer.

If the police fail to properly respect your right to counsel, it may become an important issue in your case. The court will consider whether your Charter rights were respected and whether any evidence obtained afterward can be used at trial.

7. Did the Police Make a Lawful Breath Demand

If the police require you to provide breath samples, they must make the breath demand in the manner required by law. This is an important step in an impaired driving investigation.

The police should:

• Read the breath demand using the required wording.
• Clearly explain what they are requiring you to do.
• Make sure you understand the demand.
• Make the demand at the proper time.
• Record the demand in their notes and other disclosure.

The police officer may later be asked to testify about exactly how the breath demand was made. The officer’s notes, recordings, and other disclosure may all be reviewed to determine whether the proper procedure was followed.

If the breath demand was not made properly, or there is evidence that you did not understand what the police were requiring you to do, it may become an important issue at trial.

Related: If you were charged with refusing to provide a breath sample, learn more about Refuse Breathalyzer charges and the legal requirements the Crown must prove.

8. Were the Roadside Breath Tests Were Conducted Properly

In many impaired driving cases, the police ask a driver to provide a roadside breath sample using an Approved Screening Device (ASD). This is a different device from the breath-testing instrument used later at the police station.

If a roadside breath test was given, the Crown Attorney may have to prove that:

• An Approved Screening Device was used.
• The device was functioning properly.
• The officer was authorized and trained to use it.
• The test was administered according to the required procedures.
• The roadside device was readily available and the test was given without an unreasonable delay.
• The result was recorded accurately.
• The officer’s notes and disclosure support what happened.

The defence may also review whether:

• The device had been properly maintained.
• The device had been checked or tested as required.
• There were any issues that could affect the reliability of the result.
• The officer’s notes are complete and consistent with the rest of the evidence.

Problems with the roadside breath test do not automatically result in the charge being dismissed. However, errors, inconsistencies, equipment issues, or unexplained delays may become important issues when defending the case.

Related: If you were charged with refusing a roadside breath test, different legal issues may apply. Learn more about the offence and the legal requirements the Crown must prove on our Refuse Roadside Breath Test page.

9. Unreasonable Delays Before Breathalyzer Tests

After an arrest, the police will usually take the accused to the police station so further breath testing can be completed. The time between the arrest and the breath tests can become an important issue.

The Crown Attorney needs to prove that:

• The police acted without unnecessary delay.
• The accused was transported to the testing location as soon as reasonably possible.
• There were no unexplained delays before the breath tests were taken.
• The officer’s notes accurately record the timeline of events.

The defence will carefully review the timeline, including:

• The time of the traffic stop.
• The time of the arrest.
• When the accused arrived at the police station.
• When each breath sample was taken.
• Whether any delays have a reasonable explanation.

Not every delay is a legal problem. However, unexplained or unnecessary delays may affect the Crown’s ability to prove parts of its case and can become important issues at trial.

10. Breath Tests Were Conducted on an Approved Instrument

If the police require breath samples at the police station, they must use an Approved Instrument. This is a different device from the roadside screening device used during the initial investigation.

The Crown Attorney may have to prove that:

• An Approved Instrument was used.
• The instrument was functioning properly.
• The person conducting the breath tests was qualified to operate the instrument.
• The breath tests were conducted according to the required procedures.
• The results were recorded accurately.
• The officer’s notes and disclosure support the testing process.

The defence will carefully review:

• Whether the correct instrument was used.
• Whether the person conducting the test was properly qualified.
• Whether there are any issues affecting the reliability of the testing.
• Whether the officer’s notes and disclosure are complete and consistent.
• Whether the evidence supports the breath test results.

Problems with the testing process do not automatically result in the charges being dismissed. However, if there are errors, inconsistencies, or questions about the reliability of the evidence, they may become important issues at trial.

Related: Learn more about breathalyzer tests at the police station, how they work, and the legal requirements that apply in impaired driving cases.

★★★★★ “I contacted Nicholas after being charged with an over-80 offence… He carefully reviewed the evidence and kept me informed throughout. In the end, the charge was reduced to a ticket with no criminal conviction. I am extremely thankful for the result.” — Sam G.

11. Person Conducting the Breath Tests Was Qualified

Breath tests at the police station must be conducted by a Qualified Technician. The Crown may have to prove that the person operating the Approved Instrument was legally qualified to perform the testing, and that:

• The breath tests were performed by a Qualified Technician.
• The technician followed the required testing procedures.
• The technician recorded the results accurately.
• The technician’s notes and records are complete and consistent.
• The technician is able to explain the testing process in court, if required.

The defence will carefully review:

• Whether the technician followed the required procedures.
• Whether the technician’s notes are complete and accurate.
• Whether there are any inconsistencies between the technician’s evidence and the other disclosure.
• Whether any errors could affect the reliability of the breath test results.

The fact that a Qualified Technician performed the breath tests does not automatically mean the evidence is accurate or reliable. The defence will carefully review the testing process and all of the evidence before deciding whether the Crown has proven its case beyond a reasonable doubt.

12. Two Suitable Breath Samples Were Obtained

In impaired driving cases, the police will ask you to provide two breath samples at the police station using a breathalyzer. The Crown Attorney will have to prove that the required breath samples were obtained according to the law.

• Two suitable breath samples were obtained.
• Each sample was taken using the Approved Instrument.
• The samples were collected according to the required procedures and timing.
• The results were accurately recorded.
• The technician’s notes and records support the testing process.

The defence will carefully review:

• Were both breath samples were properly obtained.
• Whether the testing procedures were followed.
• Any inconsistencies in the records or disclosure.
• The evidence supports the breath test results.

Problems with the breath testing process do not automatically mean the charge will be dismissed. However, if there are errors, inconsistencies, or unanswered questions about how the samples were obtained, they may become important issues at trial.

13. Court Documents Were Properly Prepared, Served, and Filed

An impaired driving or DUI charge involves more than police officers giving evidence in court. The Crown also relies on a number of legal documents that must be properly prepared, served, and filed.

These documents may include:

• The Information, which is the “charging document” that starts the criminal case.
• Certificates relating to the breath test results.
• Notices required by the Criminal Code.
• Police notes and occurrence reports.
• Records relating to the Approved Instrument or breath testing procedures.
• Other documents required to prove the case.

The defence carefully reviews these documents to determine whether they were completed correctly and whether the legal requirements have been followed. Errors on documents can lead to the documents being inadmissible, whereupon it can dramatically affect the outcome of the charge.

In many cases, the Crown must also prove that certain documents were served on the accused. Served means the documents were formally provided to the accused in the manner required by law. If the issue is challenged, the Crown may have to explain to the judge how and when the documents were served.

Errors, inconsistencies, missing documents, or failures to comply with the Criminal Code may affect whether some evidence can be used at trial.

14. Video Evidence Must Be Consistent With the Other Evidence

Many police vehicles and police stations are equipped with video recording systems. Depending on the circumstances, video evidence may become an important part of an impaired driving case.

Video evidence may include:

• Dashcam recordings from the police vehicle.
• Body-worn camera footage.
• Video from the police station.
• Security camera recordings from nearby businesses or homes.
• Other recordings that capture part of the investigation.

The defence carefully compares any available video with the police officers’ notes, witness testimony, and other evidence. If the video does not match what is described in the officers’ notes or their testimony, those differences may become important during cross-examination.

Video evidence does not always prove or disprove a charge. However, it can help the court better understand what happened and may reveal inconsistencies, contradictions, or missing details that affect the Crown’s case.

Every impaired driving case is different. An experienced Toronto DUI lawyer will review all available evidence, including video recordings, to determine whether they support or contradict the Crown’s case.

15. The Crown Must Provide Full Disclosure

Before your case goes to trial, the Crown must provide the defence with all the evidence it intends to rely on. This is called disclosure. It allows the defence to understand the case, review the evidence, and prepare a proper defence.

Disclosure may include:

• Police officers’ notes.
• Witness statements.
• Dashcam or body camera recordings, where available.
• Breath test records and related documents.
• Maintenance or testing records for the Approved Instrument, where relevant.
• Other evidence the Crown intends to rely on.

The defence carefully reviews every page of disclosure to identify inconsistencies, missing information, or legal issues that could affect the case. Sometimes additional disclosure must be requested before the case can proceed fairly.

If important disclosure is missing or provided late, the defence may ask the court for an appropriate remedy. In some cases, missing disclosure can affect the fairness of the trial.

Every impaired driving case is different. A careful review of the disclosure often reveals issues that are not obvious when the charge is first laid.

16. The Case Must Be Heard Within a Reasonable Time

The Canadian Charter of Rights and Freedoms guarantees that every person charged with a criminal offence has the right to be tried within a reasonable time. Unnecessary delays can affect the fairness of the court process.

When reviewing a case, the defence may consider:

• How long it took for the case to reach trial.
• The reasons for any delays.
• Whether the defence caused or agreed to any delays.
• Whether delays were outside the control of the parties.
• Whether the total delay exceeds the legal limits established by the courts.

Not every delay will result in the charges being dismissed. However, if a case has taken too long to reach trial, the defence may bring an 11(b) application under section 11(b) of the Canadian Charter of Rights and Freedoms. An 11(b) application asks the court to determine whether the accused’s right to be tried within a reasonable time has been violated. If the application is successful, the court may stay the proceedings, bringing the prosecution to an end.

Every impaired driving case follows its own timeline. Our Toronto DUI lawyers will review the history of the case to determine whether delay has become a legal issue.

17. Your Charter Rights Must Be Respected

The Canadian Charter of Rights and Freedoms protects everyone charged with a criminal offence. If police fail to respect those rights during an impaired driving investigation, the defence may ask the court to exclude evidence or grant another legal remedy.

Depending on the circumstances, the defence may examine whether:

• The traffic stop was lawful.
• The detention or arrest was lawful.
• You were informed of your right to speak with a lawyer without delay.
• You were given a reasonable opportunity to contact a lawyer.
• Police continued their investigation before your Charter rights were respected.
• Evidence was obtained in a manner that violated the Charter.

Not every Charter violation will result in the charges being dismissed. However, if the court finds that important evidence was obtained by violating your Charter rights, it may refuse to allow that evidence to be used at trial. In some cases, that can significantly weaken the Crown’s case.

A single mistake by the police does not automatically mean an impaired driving charge will be dismissed. However, courts look at the entire investigation. Several problems with the evidence or police procedures may strengthen the defence and affect the outcome of the case.

18. Witnesses Must Give Credible and Reliable Evidence

The Crown must prove its case using reliable evidence. That often includes testimony from police officers and, in some cases, civilian witnesses. Before reaching a verdict, the judge must decide whether the witnesses are credible and whether their evidence is reliable.

During the trial, the defence may examine:

• Whether the witness’s testimony is consistent with their notes.
• Differences between the evidence given by various witnesses.
• The witness’s ability to remember important details.
• How the testimony compares with the physical and documentary evidence.
• Any discrepancies, contradictions, or inconsistencies in the evidence.

Cross-examination is an important part of every impaired driving trial. It gives the defence an opportunity to question witnesses, test the accuracy of their evidence, and identify weaknesses in the Crown’s case.

Every witness can make mistakes. If the judge has a reasonable doubt about the credibility or reliability of the evidence, the Crown may not be able to prove the charge beyond a reasonable doubt.

19. The Crown Must Prove the Charge Beyond a Reasonable Doubt

In every criminal case, the Crown must prove the charge beyond a reasonable doubt. This is the highest standard of proof in Canadian law.

The judge must consider all of the evidence presented during the trial, including:

• The testimony of the witnesses.
• The documentary evidence.
• The breath test evidence.
• Any Charter issues raised by the defence.
• Any inconsistencies or weaknesses in the Crown’s case.

The defence does not have to prove that you are innocent. Instead, the Crown must prove every essential part of the charge beyond a reasonable doubt. If the judge is left with a reasonable doubt after considering all of the evidence, the accused must be found not guilty.

A successful defence often involves carefully examining every part of the Crown’s case rather than relying on a single issue. Even small problems with the evidence can create reasonable doubt when all of the evidence is considered together.

Related: Learn more about reasonable doubt in impaired driving cases.

20. The Judge Must Consider All of the Evidence Together

At the end of an impaired driving trial, the judge must consider all of the evidence before deciding whether the Crown has proved the charge beyond a reasonable doubt. The judge does not look at each piece of evidence in isolation. Instead, the entire case is considered as a whole.

The judge may consider:

• The testimony of the police officers and any other witnesses.
• The documentary evidence.
• The breath test evidence.
• Any Charter issues raised during the trial.
• Any discrepancies, contradictions, or inconsistencies in the evidence.
• Whether the evidence is credible, reliable, and consistent.

A single mistake or inconsistency may not be enough to create a reasonable doubt. However, when several problems appear throughout the Crown’s case, the judge must consider their combined effect. Small errors, conflicting evidence, missing information, or unreliable testimony may weaken the Crown’s case when viewed together.

Every Impaired Driving Case Deserves a Careful Review