Rich Leotta holds a photo of his son, Montgomery County police officer Noah Leotta, who was killed in December when a drunk driver struck him, on Feb. 10 in Annapolis. (Ricky Carioti/The Washington Post)

IT TOOK a perfect storm of good timing, tragic events and tenacious advocates, but finally Maryland has started to overcome the retrograde forces in Annapolis that for years blocked no-nonsense laws to control drunken driving.

In the closing hours of this year’s legislative session, those forces combined to impel, and shame, Maryland legislators into passing a bill that significantly expands the use of ignition interlocks, dashboard devices that prevent vehicles from starting if the driver has had too much to drink.

The legislation was spurred by the death of a young police officer in Montgomery County, Noah Leotta, who died after being struck by a suspected repeat drunk driver on Rockville Pike last December while on patrol to catch just such offenders. Mr. Leotta was one of 50 Montgomery County officers to be struck by a drunk driver in the past three years. Many people, including Mr. Leotta’s parents, worked hard to ensure his death would not be in vain.

The resulting legislation, known as “Noah’s Law,” was similar to previous bills that had been buried in the Judiciary Committee of the House of Delegates, where harrumphing lawmakers seemed concerned with protecting drunk drivers more than their victims. This year, with anti-drunken-driving advocates dedicated to the memory of Mr. Leotta, the dynamic in Annapolis changed. No longer could legislators mumble about the unfairness of imposing dashboard Breathalyzers on offenders who were just “one sip over the line.”

The measure toughens existing law considerably. Under current law, ignition interlocks are optional, and easily avoided, for run-of-the-mill drunk drivers. They are imposed mainly on repeat and youthful offenders, or those who are inebriated to the point of incoherence, with a blood alcohol content of 0.15.

Under Noah’s Law, the devices, which have proved highly effective, will be required for drivers who meet the legal definition of drunk, meaning 0.08 or higher. The interlocks, which require the driver to prove his sobriety by blowing into a tube before the car will start, will be imposed for six months upon conviction, or nine months should a driver refuse to take the breath test. The number of devices installed in Marylanders’ cars (at the drivers’ expense), currently around 11,000, could increase substantially.

The public outcry about drunken driving in this country has faded over the past couple of decades, but it was revived in Maryland for Noah’s Law. Joining Mr. Leotta’s parents as eloquent and compelling advocates for tougher laws were activists from Mothers Against Drunk Driving, police officials including Montgomery County Chief J. Thomas Manger, and lawmakers such as Del. Benjamin Kramer (D-Montgomery).

In the House of Delegates, Speaker Michael E. Busch (D-Anne Arundel) made it clear to the Judiciary Committee chairman, Joseph F. Vallario Jr. (D-Prince George’s), who has routinely blocked such legislation, that the jig was up. At last, lawmakers were ready (or forced) to reckon with the fact that about one-third of the traffic deaths in this country still involve drunk drivers — one sip over the line or not.