BALTIMORE, JAN. 29 -- Former Maryland state senator Clarence M. Mitchell III was found guilty tonight of conspiracy and obstructing a federal grand jury investigation into his business ties to a convicted Baltimore drug kingpin.

Flanked by his attorney and his mother, Mitchell, 48, whose family spawned a black political dynasty in Maryland, stared solemnly at the jurors as they pronounced him guilty on one count each of conspiracy and obstruction of justice. The verdicts were reached after 11 1/2 hours of deliberation.

The conviction was the Democratic politician's second on felony charges in little more than two months. In November, he and his brother, state Sen. Michael B. Mitchell, 42, were convicted of accepting $50,000 to stop a congressional probe of the New York-based Wedtech Corp. conducted by their uncle, then-Rep. Parren J. Mitchell.

The brothers had been scheduled to be sentenced today on the Wedtech corruption charges, but U.S. District Judge Norman P. Ramsey decided to postpone the action until next week because the jury was still deliberating Clarence Mitchell's case by late afternoon.

Clarence Mitchell faces a maximum prison term of 20 years from the two convictions, while Michael Mitchell could be sentenced to a maximum of 15 years for the Wedtech case. The Mitchells could also be forced to pay hundreds of thousands of dollars in fines.

Standing on the steps of the courthouse, Clarence Mitchell vowed to fight both rulings.

"This is just round one and I don't feel in any way tired," he said. "This just means God wants us to keep on exposing what's going on."

Since their indictments last year, the Mitchells, the sons of prominent civil rights activists Juanita Mitchell and the late Clarence M. Mitchell Jr., have maintained they are the victims of a Reagan administration plot aimed at discrediting black leaders.

Clarence Mitchell renewed those charges today, lambasting Attorney General Edwin Meese III for his alleged role in the Wedtech case, alleging that federal prosecutors had intimidated the jury, and comparing himself to the Rev. Martin Luther King Jr.

"Martin Luther King was found guilty over and over again and yet he was ultimately vindicated," Mitchell said. "They killed Martin Luther King. They are just lynching me legally."

Michael Mitchell, a lawyer who had participated in his brother's defense, said he thought it was a "strange coincidence" that they were charged in the Wedtech case on April 4 of last year, the anniversary of King's assassination.

Maryland U.S. Attorney Breckinridge L. Willcox said he had known the Mitchell family a long time and called the comparisons to King "very sad."

"Neither Ed Meese nor Ronald Reagan or anyone with a racist vendetta was sitting in that jury box," Willcox said. "It was the citizens who have rendered judgment against Clarence Mitchell."

During the two-week trial, Clarence Mitchell was accused of hampering a grand jury investigation of convicted drug trafficker Melvin D. (Little Melvin) Williams. Prosecutors alleged Mitchell gave them false papers indicating he got a $15,000 loan from Baltimore businessman Jerry L. Hill to hide between $50,000 and $83,000 he actually received from Scrapp Investment Co., a company Williams controlled.

Prosecutors said that Mitchell was paid the money -- and then tried to cover it up to avoid paying taxes -- as a fee for helping Scrapp obtain city funds to rehabilitate a West Baltimore apartment complex in October 1983.

Although Mitchell testified that he had received only $5,000 for his part in the ill-fated deal, Scrapp President James E. Rogers said the influential politician had been paid $83,000. Additionally, Hill -- the businessman Mitchell said had given him the loan -- testified under immunity that no such transaction had ever taken place.

Clarence Mitchell faces three additional trials in coming months on charges of padding his expenses as a state senator by $12,000, falsifying information on a government-guaranteed loan for an employee of his real estate business, and failing to pay taxes on $101,000 in income in 1984 and 1985.