BAC Limits in Michigan

Device used to obtain someone's blood alcohol content (BAC) reading [insert number] which is the BAC limit for a standard OWI charge in MichiganUnderstanding blood alcohol content (BAC) limits is important if you are facing drunk driving charges or are not sure what the legal guidelines are surrounding drinking and driving. In Michigan, the BAC limit is below 0.08, which means if a person tests at or above that amount, they will be charged with a drunk driving offense. Even if you are below this limit, you can still be charged with drunk driving if the arresting officer deems your driving to be impaired by alcohol by observation or a field sobriety test. Because of this additional grey area, understanding Michigan’s BAC limits and DUI in general can be difficult.

In many cases, the simplest question a person might ask in regards to BAC limits will be how many drinks it takes to reach the legal limit of 0.08. Unfortunately, the answer is not simple and takes some understanding of bodily composition, alcohol absorption rates and general physiology. Being able to understand this fully allows DUI defense attorneys to properly represent their clients and ensure they are defended from unfair or even improper charges.

Physiological Factors

There are multiple physiological factors that come into play when determining how the body absorbs, processes and is affected by alcohol.  The main factor in this is what gender the person is, as alcohol is processed in the body at different rates between men and women. This is due to differences in liver size as well as body fat percentages and water content between the two genders.

Women naturally have higher body fat content, which aids in keeping alcohol in the bloodstream longer than men. Alcohol gravitates towards water, and because of a higher fat content, it has less water to dilute into. Generally speaking, if a man and a woman of equal weight consume an equal amount of alcohol, the woman will have a higher BAC for a longer period of time.

While modern science explains this phenomenon, in the past conventional wisdom held that the reason for women becoming intoxicated quicker is that they simply eliminate alcohol slower than men. However this is not the case. In fact, the average BAC elimination rate for men is 0.015 per hour, whereas the average rate is 0.018 per hour for women – which means their livers are technically more efficient at eliminating alcohol than men. This seemingly conflicting information can be confusing on the surface, but is explained by a woman’s higher fat content per body weight as mentioned previously. This is the real reason for the higher BAC in women – there is less water for the alcohol to dilute into.

The lower fat content per body weight in men, combined with their larger average body size compared to women means that the same size drink in an average man and an average woman has quite different effects in terms of BAC levels over time. Even with women’s more efficient livers, they are at an overall disadvantage when it comes to the speed at which alcohol is eliminated. This balance is important to understand when analyzing and defending drunk driving cases.

Additional BAC Factors

In addition to gender based differences in BAC levels, there are several other factors that affect the rate at which alcohol is absorbed and metabolized by the body. These include:

  • The rate at which alcohol is consumed, normally measured in drinks per hour
  • The amount of food consumed prior to and during the process of drinking
  • Prescription medications that may be taken concurrently
  • What time of the day the alcohol was consumed
  • Smoking habits
  • Using birth control or hormone pills
  • Being tired, sleep deprived or fatigued

Measured Units of Alcohol and BAC

Alcohol consumption is best measured by units, not by the drinks themselves. This is due to varying amounts of alcohol content in different types of drinks. It is important to understand this as several drinks of one type will result in quite different BAC levels than another. Below are the general guidelines for what constitutes a single unit of alcohol per drink type:

  • 5-6 oz of wine with a 12% alcohol content
  • 12 oz of beer with a 5% alcohol content
  • 1.5 oz of 80 proof liquor

Averaged out between men and women, a single unit of alcohol will raise BAC levels by 0.02 to 0.025.

Special BAC Circumstances and Limits

There are certain circumstances in Michigan where special BAC limits outside of the standard 0.08 apply. These are applicable for situations involving High BAC OWI, Minor OWI and CDL holder OWI. In these situations, the gravity of the offense creates the need for extra strict BAC limits and punishments beyond normal OWI cases.

If a person is pulled over in Michigan and has a measured blood alcohol content of 0.17 or higher, they can be charged with a “high BAC OWI” offense, also known as a super drunk charge. A conviction for this carries with it significantly increased penalties in the form of heavy fines and extended jail time. The reason this is treated differently than a standard OWI offense is the severity of accidents that occur as a result of drivers with a high BAC. The goal of the increased punishment is to have stronger discouragement from such reckless behavior.

Blood alcohol content limits for minors in Michigan is considered “zero-tolerance”, which means that the state does not allow for any consumption of alcoholic beverages by minors prior to or during driving. This is in addition to the general prohibition of alcohol for those under 21 years of age. In order to account for normal background and natural BAC levels present in the body, the state has set the limit at 0.02% for minors. Anything at or above this level will result in a drunk driving arrest.

The last special limit for blood alcohol content set by the State of Michigan is for CDL holders. Due to the nature of operating commercial vehicles and the increased risk they pose to other motorists on the road, the BAC limit for CDL holders operating commercial vehicles is 0.04% – half that of normal passenger vehicles. While this limit only applies to CDL holders actively operating commercial vehicles, it should be noted that a OWI conviction outside of this can have implications on their commercial driving privileges.