Mirza H. Baig, the Laurel physician and developer who paid tens of thousands of dollars in bribes to then-Prince George’s County Executive Jack B. Johnson, was sentenced Thursday to 18 months in prison.

Baig, a longtime associate of Johnson (D), was captured by FBI video surveillance handing Johnson $15,000 in cash. That proved to be a key moment in a federal corruption probe in Prince George’s that led to the arrests of Johnson and his wife, Leslie Johnson, then newly elected to the County Council.

After Baig, who was cooperating with federal authorities, handed Jack Johnson the cash, agents listening in on a wiretap overheard the county executive and his wife discussing ways to destroy evidence. As investigators pounded on the door of the Johnsons’ Mitchellville home, the couple concocted a plan for Leslie Johnson to flush a $100,000 check from Baig down the toilet, and stuff $79,600 in cash in her underwear.

According to prosecutors, Baig paid Jack Johnson and county housing director James E. Johnson between $400,000 and $1 million in bribes over time as they helped Baig obtain county property and gain access to federal housing funds. James and Jack Johnson are not related.

Baig, 68, who pleaded guilty last year to conspiracy to commit extortion, faced a maximum five-year sentence. But at the hearing in U.S. District Court in Greenbelt, prosecutors asked for leniency, saying Baig helped build the case against the Johnsons. In addition to the 18-month sentence, U.S. District Judge Peter J. Messitte ordered Baig to forfeit $250,000 and imposed a $50,000 fine. Baig will also have two years of supervised release when he leaves prison.

“You were involved in significant corruption yourself,” Messitte said. “Not only should you have known better, you knew better. . . . You were bribing public officials for your benefit. You wanted things and in exchange you got them.”

“This is a serious matter,” said Messitte, who cautioned Baig that he could not “say, ‘I am sorry and continue my life in the community.’ The community will not stand for that.”

Baig, whose company Baig Ventures had been in the development business for at least 20 years, was a well-known figure in Prince George’s and Montgomery County political circles. For years he donated to the campaigns of Maryland politicians, even after he entered a sealed guilty plea on April 11, 2011, six months after the Johnsons’ arrests.

He began cooperating with federal authorities about two weeks before the Johnsons’ arrests, twice paying Jack Johnson bribes as federal agents monitored him.

Baig was Johnson’s personal physician and counted other local politicians among his patients at Laurel Lakes Primary Care.

According to Jack Johnson’s guilty plea, from 2003 through at least Nov. 12, 2010, he and housing director Johnson were part of a conspiracy in which Baig, developer Patrick Ricker and others offered money, trips, employment, mortgage payments and campaign contributions.

Federal prosecutors said that in exchange for the bribes, Jack Johnson, James Johnson and other still unnamed county officials helped developers and business owners, including obtaining a waiver of federal housing regulations and securing millions in federal housing funds.

Under questioning from the judge, Assistant U.S Attorney A. David Copperthite said Baig walked away from one development with $1.2 million, double his investment. He was “bailed out of other investments because of his corrupt relationship with Jack Johnson,” Copperthite said.

Baig apologized in court, saying he had been friendly with Johnson for years and fell into a situation that he regretted.

“It was my mistake of being ignorant,” he said.

Jack Johnson is serving a seven-year prison term. Leslie Johnson (D), who was poised to head a key committee overseeing development at the time of her arrest, is serving a one-year sentence. James Johnson is to report to prison June 1 for a three-year sentence.

U.S. Attorney Rod Rosenstein said that the investigation of corruption in Prince George’s continues.

“Anyone who had been involved in corruption in Prince George’s County is not in the clear,” he said after Baig’s sentencing.

“We have not closed the book on corruption related to Jack Johnson.”