What is a “prior offense” of DUI in Pennsylvania?
Determining whether or not a person has a “prior offense” is extremely important in Pennsylvania DUI cases because prior offenses substantially increase the severity of the DUI charge and thereby directly impact the range of sentences, including jail time, fines, and license suspensions, that a person will face. What is considered a “prior offense” for DUI charges in Pennsylvania has changed over the years. What may have been the law a few years ago may not be the law of Pennsylvania now.
Interpreting 10-Year Look Back Window
It must be emphasized that there is a difference between prior offenses for mandatory minimum sentencing purposes and prior offenses overall. For mandatory sentencing purposes, the court considers prior DUI offenses from the past 10 years. Many people think that a prosecutor or judge is not permitted to consider any DUI offenses that occurred more than 10 years ago. That is NOT the law. Prosecutors and judges are permitted to consider a person’s entire criminal record, both DUI and non-DUI offenses that occurred more than 10 years ago. The 10-year look back 
window applies to whether or not the current offense is considered a second, third, or subsequent offense for mandatory sentencing purposes.
The case of Commonwealth v. Mock defined the 10-year look back period of time as being from the date of conviction or ARD acceptance for the prior offense until the offense date on the new case. This means that at the time of sentencing on a DUI case, the judge looks at when the person was arrested for DUI on the current case, goes back 10 years into the past, and every DUI sentencing or ARD placement within that time frame is counted as a prior offense. It is the date of sentencing on a prior DUI and not the date upon which the person pleaded guilty.
For example, assume that a person has 3 total DUIs, with sentencing on the first being January 1st of 2004, sentencing on the second being June 1st of 2012, and the arrest on the third being June 1st of 2018. Note that the important date for the pending DUI is the arrest date, meaning the date upon which the person drove while under the influence. In this hypothetical, the current DUI would be a second offense for mandatory minimum sentencing purposes because the person would have one prior offense within the past 10 years. The first offense would not be considered a “prior offense” for mandatory minimum sentencing purposes because it was beyond 10 years, but the sentencing judge could still consider that this was the person’s third lifetime DUI.
ARD is a “Prior Offense”
NOTE – On May 20th of 2020, the Pennsylvania Superior Court issued two decisions in Commonwealth v. Chichkin and Commonwealth v. Roche holding that the law that made an ARD disposition a “prior offense” was unconstitutional. To read more about this issue, check out this blog article. The precise impact of this decision is not yet completely known as some prosecutors are trying to find ways to circumvent the decision and still use an ARD disposition as a “prior offense.” It is extremely important that a person with a prior ARD hires a good DUI attorney to provide representation based upon decisions like this. Whether or not the prior ARD case was expunged may be of critical importance.
Out-of-State DUIs as Prior Offenses
Pennsylvania does consider out-of-state prior DUIs as prior offenses if the other state’s drunk driving law are “substantially similar” to Pennsylvania’s DUI laws. There are many Pennsylvania cases that have interpreted DUI laws from states like New York and New Jersey and found that those states’ law are substantially similar. In a rare case, a Centre County judge did rule that a Virginia DUI law was not substantially similar. By ruling that the law was not substantially similar, the prior Virginia DUI conviction was not considered a prior offense. At this point, most states have passed DUI laws that are similar to Pennsylvania drunk driving laws, so most out-of-state DUI convictions will be considered prior offenses.