A recent impaired driving arrest raises some important issues that people in Ontario should understand with regard to breath tests.First, it is important to know that refusing a breath test is a crime in Ontario, and that breath test refusal can result in serious penalties. Those may include suspension of your driver's licence for a year, a fine, required alcohol counselling and much higher insurance rates. Refusing to provide a breath sample can also result in a criminal record and employment issues.Police officers use breath tests to determine whether drivers are impaired. If a breath test indicates that a driver has a blood-alcohol level over 80 milligrams per 100 millilitres of blood, then the driver may be charged with drinking and driving.However, depending on the facts of the case, there may be effective defences against charges of driving over 80 or charges of breath test refusal.For example, a driver may have a medical condition that limits lung capacity and prevents the driver from performing a breath test. A defence may also be based on mistakes made by police, such as lack of reasonable suspicion to stop the driver or failure to properly administer the sobriety tests. There is also something called the "Last Drink Defence," which is sometimes referred to as the "Rising Blood Alcohol Defence."The recent arrest that brings these issued to mind involved a driver who, according to police, tried to affect the results of a breath test by placing a penny in his mouth. A misconception persists that putting a penny or some other coin in one's mouth can trick a Breathalyzer. In this case, the officer reportedly asked the man to remove the penny, but the man swallowed it.Now, in addition to being charged with impaired driving, the man is charged with obstructing a peace officer because he allegedly swallowed the coin. It remains to be seen whether the prosecution has sufficient evidence to convict the man on either charge.For more on defence strategies for driving over 80 charges, please see Neuberger & Partners' impaired driving overview.