A “Support Noah's Law” button is worn during a MADD news conference Wednesday. (Ricky Carioti/The Washington Post)

Rich Leotta sat surrounded by Maryland lawmakers Wednesday, struggling to make it through a news conference before tears began to fall.

He talked about his son Noah, a 24-year-old police officer who was killed by a driver suspected of being drunk two months ago, and about “Noah’s bill,” a measure that would require more drunk drivers to use an ignition lock on their cars after being convicted of driving under the influence.

“I really don’t understand why such a commonsense law hasn’t passed,” said the elder Leotta, holding up an ignition “interlock” and trying to push down emotions that bounced from sorrow to anger. “The state of Maryland needs to do better. The nation needs to do better.”

Leotta was joined by officials from Mothers Against Drunk Driving who released a report Wednesday that showed that interlocks, which require motorists to breathe into a tube before they can try to start their vehicles, have stopped 1.8 million cases of drunken driving nationwide. MADD is calling for a wider use of the technology.

A large American flag flies over Georgia Avenue in Olney as the procession for Montgomery County Police Officer Noah Leotta moved to the Judean Memorial Gardens from the Covenant Life Church in Gaithersburg. Leotta was killed by a suspected drunk driver while on duty in December. (Michael S. Williamson/The Washington Post)

The national organization dedicated the report’s findings to Noah Leotta, who was struck in Montgomery County while working a special detail aimed at getting drunk people off the road.

“Ignition interlocks save lives, and they could save even more lives if every offender is required to use the device after the first arrest,” said Colleen Sheehey-Church, the group’s president.

Using data from interlock device companies, MADD added up the number of times the ignition-lock devices stopped someone who was legally drunk from starting a car.

“The fact that so many people have attempted to drive impaired — even after being caught and ordered to use an ignition interlock — tells us that we must put technology between all offenders and their cars,” Sheehey-Church said.

The group found that every state uses the devices, although the terms and frequency vary. About half of states mandate the ignition locks for those convicted of driving at or above the legal blood-alcohol limit of 0.08 percent. That level is the equivalent, MADD said, of a 160-pound man drinking four beers in an hour.

In other states, mandatory use of the devices kicks in at higher blood-alcohol levels. The devices cost about $70 to $150 to install, according to MADD, and about $60 to $80 per month for monitoring and calibration.

In Maryland, where Noah Leotta was an officer for the Montgomery County Police Department, drivers convicted of driving with a blood-alcohol content of 0.15 percent or higher must have an interlock device installed on their vehicles to avoid having their licenses suspended.

Maryland motorists convicted of drunken driving with lower blood-alcohol levels — from 0.08 percent to 0.14 percent — can still enroll in the state’s interlock program. But unless a judge orders a person to do so, the program is not mandatory, and voluntary participation requires attending a $150 administrative hearing, said a spokesman for the Maryland Motor Vehicle Administration.

Under regulations expected to take effect soon, those convicted at the lower blood-alcohol levels would be able to enter the interlock program without attending the hearing. But it still would not be required.

Del. Benjamin F. Kramer and Senate Majority Whip Jamie Raskin, both Democrats from Montgomery County, are leading this year’s effort to expand the use of interlock devices in Maryland.

The lawmakers blamed the strong liquor lobby in Annapolis for similar bills failing to get out of committee in past sessions. Raskin said a mandatory ignition interlock bill was first introduced in 2009.

“Of the thousands of bills that we will consider this year, this is the only one that we can say for a fact is going to save lives,” Kramer said. “We’ve got to move this forward.”

The American Beverage Institute, a trade organization that represents restaurants, said that while interlocks are a valuable part of DUI enforcement, they should be reserved for the most serious offenders — those with high blood-alcohol content.

“It’s a great tool to go after hard-core drunk drivers,” said Sarah Longwell, a spokeswoman for the group. “But someone who is one sip over the legal limit shouldn’t automatically be treated the same as high-BAC offenders and repeat offenders.”

Noah Leotta was working a holiday drunken-driving task force Dec. 3 when he pulled over a car in Rockville. While he was outside his cruiser, another car struck him from behind. The driver, Luis Reluzco, 47, had been drinking, according to police reports and officials. He has not been charged; police are continuing to work on the case and have said they suspect he was drunk.

Rich Leotta said drunk drivers killed 130 people in Maryland last year. “These other 129 people are also very special but do not have the voice Noah has been given,” the elder Leotta said. “So Noah is representing all the people of Maryland, and throughout the country, that have been needlessly killed and injured by drunk drivers.”