Montgomery County prosecutors on Monday dropped more than 30 charges against a Damascus couple and their two sons who were accused of hosting a underage keg party, ending a case that has raised questions about whether county police have become too aggressive as they try to crack down on teenage drinking.

The move by prosecutors came after Circuit Court Judge Steven Salant ruled that officers had improperly slipped into the back yard of George and Cathy Magas the night of Jan. 4. Salant said the observations they subsequently made, and the evidence they subsequently collected, could not be used in court.

“There was an unlawful invasion of the defendants’ property,” Salant said from the bench last week.

At issue are the actions of a specially trained group of officers that puts a focus on parties at which teens are consuming alcohol. Police authorities said the unit’s efforts are necessary to address concern throughout the county about underage drinking.

“There have been too many drunk-driving deaths in this county,” Police Chief J. Thomas Manger said. “This unit is potentially saving lives every time they go out and do their jobs.”

Manger declined to comment specifically on Salant’s decision but said it is rare that judges make such rulings on the unit’s work. He said he and his commanders will review Salant’s ruling and, if appropriate, address it in their training.

The case stems from the actions of alcohol enforcement officers on the night of Jan. 4, after a Papa John’s driver delivered four pizzas to the Magas house and then sent a text message to a police officer he knows.

“Hey man, not sure if you’re working,” he began, according to court records, giving the Magases’ address and writing that he had seen “some young-looking people with beer.”

That information was passed on to alcohol enforcement officers, who soon began converging near the house — a large home at the end of a long driveway off Damascus Road. Two of the officers positioned themselves on a church property near the Magases’ back yard, according to court papers.

That is when stories start to differ.

According to prosecutors, the officers could see what appeared to be people under 21 holding red plastic cups and one of them urinating outside. The officers walked through a group of trees into the back yard, looked down an exterior stairwell, and saw several people holding cans of beer, standing near cases of beer and standing next to a half-keg. The officers asked for identification, confirmed that three were under 21 and began writing citations and trying to confiscate the half-keg and the cases of beer.

About this time, according to the prosecutors, two other officers went to the front of the house, knocked on the door, told George Magas — a certified public accountant who is well known in the Damascus community — they had received a complaint of underage drinking inside and asked if they could come in. Magas said no, according to prosecutors, eventually adding: “Do you see this house?! This is a sign of success and something that you’ll never be able to afford!”

Magas then closed the door, according to prosecutors, went through the house, exited the rear door into the back yard, punched one of the officers there in the face and wrapped his hands around another officer’s gun, unsuccessfully trying to pull it out.

By the time the night was over, police had charged Magas with more than a dozen crimes, including trying to disarm a police officer and allowing underage people to consume alcohol. Police also charged his wife and two of their sons.

From the beginning, the Magases, who have been longtime civic boosters, and their defense attorneys said they thought the accusations were excessive and in some cases completely false. Magas never mentioned the size of his house to police or their relative levels of success, never punched an officer and never tried to grab the officer’s gun, according to Rene Sandler, one of his defense attorneys.

As the case proceeded to trial, Sandler and other defense attorneys on the case, Terrell Roberts and Chris Griffiths, began going through the steps that led the two officers into the Magases’ back yard. Their conclusion: While the two were on the church property, they never saw anything suggesting an emergency and had no lawful right to slip forward through the trees into the yard.

That question — were the police lawfully allowed into the back yard — was a key argument during an all-day hearing earlier this month.

Salant delivered his ruling Nov. 10, siding with the Magases. He spoke of the areas near the back door and all the evidence spotted there. “Courts have treated this area as an extension of the house and as such subject to all the privacy protections afforded in a person’s home under the Fourth Amendment,” Salant said from the bench.

In a statement, prosecutors said that, because of the judge’s ruling, they “would have virtually no evidence to present in the case.”

Sandler said the alcohol enforcement officers need to reassess their approach to going onto properties.

“They do important work, necessary work, but they lack a basic understanding of the law,” she said.

Sandler said she has represented youths in more than 100 party cases over the past 15 years. She said that in a dozen cases, officers also have charged the parents, including doctors, lawyers and teachers.

Others familiar with the officers say they often have to make quick decisions and are willing to err on the side of public safety.

“Our party scene is a disaster. Binge drinking is a disaster,” said Maura Lynch, a former prosecutor turned local defense lawyer who has represented youths in these cases. She said she could not comment specifically on Salant’s ruling but said the officers are motivated by drunk-driving wrecks and teens ending up in the hospital.

“They know the horrible things that can happen when teenagers get drunk,” Lynch said.