Maryland's DUI and DWI laws are codified in §21-902 of the Transportation Article of the Maryland Code.  §21-902(a)(1) and §21-902(a)(2) prohibit Driving while Under the Influence of Alcohol (DUI) and Driving while Under the Influence of Alcohol Per Se (DUI Per Se).  The maximum penalty for a first violation of DUI or DUI Per Se is one year of incarceration and a $1000 fine.  It is extremely rare for anyone convicted of a first offense to receive anything close to the maximum sentence.

§21-902(b) prohibits Driving while Impaired by Alcohol (DWI).  This is a lesser offense than DUI or DUI Per Se.  The maximum penalty for a first violation of DWI is 60 days of incarceration and a $500 fine.  Once again, it is extremely rare for anyone convicted of a first offense to receive anything close to the maximum sentence.

If the State is able to prove that a person was operating a motor vehicle with an alcohol concentration of .08 or higher, then that person is guilty of the crime of DUI Per Se.  If a suspected DUI or DWI driver refuses to blow into the breathalyzer at the police station, then the State will attempt to prove either Intoxication or Impairment by other means, specifically, driving behavior, performance on Standardized Field Sobriety tests, and other indicators of impairment/or intoxication.

§27-101 of the Transportation Article of the Maryland Code imposes additional penalties for multiple offenders.  If a person is convicted of a violation of DUI within 5 years of a prior conviction, there is a mandatory minimum 5 day jail sentence imposed by this section.  This section also increases the maximum penalty for a second DUI to two years of incarceration and a $2000 fine.  The maximum penalty for a third DUI is three years of incarceration and a $3000 fine.  The maximum penalty for a second or subsequent DWI is one year of incarceration and a $500 fine.  As with first offenders, it is extremely rare for anyone convicted of DUI or DWI in Maryland to receive anything close to the maximum penalty allowed by law.

In addition to incarceration and fines, Judges can order a person convicted of DUI or DWI to complete probation, community service, home detention, and attend at a Victim Impact Panel (usually put on by Mothers Against Drunk Driving).

A conviction for a DUI or a DWI can trigger additional sanctions against a persons drivers license.  §16-205 of the Transportation Article allows the MVA to suspend a persons drivers license for a conviction of a violation of $21-902.  The length of time of the suspension, and the possibility of a modification of the suspension to allow limited driving depend on the precise charge which a person was convicted of, and on that person's criminal history.

Most first offenders in Maryland qualify for Probation Before Judgment (PBJ) under §6-220 of the Criminal Procedure article of the Maryland Code.  A PBJ will keep the criminal conviction off a person's record.  This means that there are no further penalties against a persons drivers license, and their auto insurance rates are not affected.  A PBJ is not considered a conviction under Maryland law.