BOSTON (AP) _ A grand jury on Thursday indicted the brother of the late Charles Stuart on obstruction-of-justice charges in the highly publicized shooting death of Stuart's pregnant wife in October 1989.

The Suffolk County grand jury indicted Matthew Stuart for conspiracy to obstruct justice and compounding a felony, authorities said. A friend, John McMahon, was indicted as an accessory to murder after the fact.

Implicit in the charges is the grand jury's belief that Charles Stuart killed his wife, Carol, the night of Oct. 23, 1989, said David Rodman, spokesman for the district attorney's office.

The case at first appeared to be the story of a loving couple whose lives were shattered by a nightmarish attack. But it developed into a twisted tale of a man's alleged plot to kill his wife.

Charles Stuart, who was also shot that night, told police he and his wife were attacked by a black mugger after they left a childbirth class at a Boston hospital. His gripping description of the attack in an emergency call from his car phone was repeated across the country.

The couple's prematurely born son died 17 days later.

A black man was implicated in the case, which raised racial tensions in Boston and called into question the fairness of news media and police. Some black leaders complained that police and reporters were too willing to believe that Stuart and his wife were shot by a black person.

More than two months later, Matthew Stuart came forward and told police that his brother staged the crime. Charles Stuart then became the prime suspect, and he plunged off Boston's Tobin Bridge on Jan. 4, 1990, an apparent suicide.

While authorities said Matthew Stuart was an accomplice, Massachusetts law prevents a family member from being charged as an accessory after the fact.

In his story to police, Matthew Stuart said he believed he was assisting in a possible insurance scam when he agreed to meet his brother in Boston's Mission Hill neighborhood.

Matthew Stuart said his brother handed him a bag containing Mrs. Stuart's purse, her engagement ring and a gun.

Matthew Stuart reportedly then met McMahon, and the two disposed of the murder weapon in the Pines River in Revere, north of Boston.

Matthew Stuart and McMahon were also charged with concealing stolen goods and unlawfully carrying a firearm.

Matthew Stuart faced an additional charge of conspiracy to defraud an insurance company. McMahon was also charged with conspiracy to obstruct justice.

The two were scheduled to be arraigned Friday.

''We plan to fight this,'' said Nancy Gertner, Matthew Stuart's lawyer, who noted that her client pointed authorities to Charles Stuart in the first place.

''Had Charles Stuart lived, there is no doubt, there can be no doubt, that Matthew Stuart would never, never be prosecuted,'' Gertner said.

Walter Underhill, McMahon's attorney, said he expects his client to exonerated.

''I think it is an unfortunate travesty of justice that what has been described as a runaway grand jury has attempted to make anyone, regardless of their innocence, pay for the death of Carol Stuart,'' Underhill said.

Richard Clayman, a lawyer for other Stuart family members, said they ''are obviously concerned and interested in the welfare of Matthew, whom they love. They are in his corner. It is another blow to them and continual stress. But they are relieved that the investigation is coming to an end.''

Based on Charles Stuart's original description, police identified another man, William Bennett, as a suspect. Suffolk County District Attorney Newman Flanagan said Thursday there were no plans to charge Bennett.

Bennett refused to testify Thursday before the grand jury, after newspaper reports said a witness saw someone resembling Bennett speaking with Stuart hours before the shooting.