Keith Arnez Boone, who was supposed to be confined to his home on a cocaine charge, was firing at a drug dealer when he shot and fatally wounded Dona Elizabeth Ferguson, 40, as she was hanging curtains in her home last year, a Prince George's County prosecutor told a jury yesterday.

Assistant State's Attorney Robert L. Dean, laying out the state's case against Boone on first-degree murder charges, called Ferguson's June 16 death "a senseless killing" and said it occurred because Arnez was trying to avenge the beating of a buddy a day earlier.

Instead, Dean said, the bullet Boone shot struck Ferguson in her left side as she stood at her window and exited from her right side. Her 9-year-old son found his mother lying in a pool of blood and ran next door to a neighbor crying out, "Momma's been shot!"

Prosecutors allege that Boone was shooting at Norman Bonds, who sold crack cocaine in the parking lot of the Fox Glen apartment complex in Capitol Heights, near where Ferguson lived. A day earlier, Bonds had beaten up a friend of Boone's, Ronald Degaulle Rice Jr., 33, of Capitol Heights, during an argument over a drug deal.

According to court records, prosecutors allege that Rice's father, Ronald Degaulle Rice Sr., 60, drove a white Nissan Maxima into the parking lot where Bonds sold drugs, and Rice Jr. got out of the car with a baseball bat while Boone got out with a gun. The Rices have told investigators that Boone fired the shot, according to law enforcement sources.

But Boone's attorney, Douglas J. Wood, told the jurors in Prince George's Circuit Court that there are holes in the police investigation. Wood said Boone's fingerprints were not found in the car in which police said he rode before the shooting. He noted that police initially believed that one of Boone's codefendants was the gunman and even sought an arrest warrant for him. And, Wood said, a key prosecution witness first told police someone else had fired the shot.

"Police had to backtrack. They had a witness problem," Wood said. "They had to make the evidence fit Keith Boone."

Boone's arrest in Ferguson's slaying focused attention on problems with home detention firms in Maryland and especially in Prince George's County.

Last January, Boone, 21, was sentenced to a year of home detention after being convicted of cocaine possession. Less than three hours after he is accused of shooting Ferguson at 6:20 p.m., Boone answered the phone in his Beltsville apartment. And about 6 1/2 hours after that, Boone again answered the phone.

Both calls were from a private home detention firm that was checking to make sure Boone was home and not out on the streets; by answering the phone both times, Boone avoided any violation of his home detention sentence.

The case sparked criticism by some state lawmakers who demanded stricter controls on home detention firms and tighter supervision of people they monitor. The firm that was supervising Boone went out of business late last year after reports filed under new state requirements showed that they had the majority of all supervision problems in the state.

Bonds, who police say was Boone's target, was the prosecution's first witness yesterday. He testified that the younger Rice asked to buy a "dime," a $10 amount of crack cocaine, on June 15. Bonds testified that he didn't have dimes, only larger amounts that sold for $20, but that he broke one in half for Rice Jr. When Rice Jr. veered off toward another drug dealer, Bonds testified that he became testy and suggested to Rice Jr. he didn't like having one of his crack rocks broken in half.

At that point, Bonds testified, Rice Jr. walked over and "sucker-punched" him, but he recovered and beat Rice Jr. unconscious.

The next day, Bonds testified, he was in his usual spot in the parking lot of the apartment complex, selling drugs, when a white Nissan Maxima pulled up and two men got out, one of them wielding an aluminum bat. When he recognized the man with the bat as Rice Jr., he ran through the parking lot toward Walker Mill Road, Bonds testified.

As he ran, he turned and saw the other man--who prosecutors say was Boone--pull a gun from his shirt. Bonds, 20, testified that he zig-zagged through the parking lot across the road and into some woods and heard a shot as he left the parking lot. Boone testified that he picked Boone out of a photo array as the shooter.

During his cross-examination of Bonds, Wood suggested that when police questioned him about the shooting, he initially identified the photograph of a Rice relative as the gunman. Bonds, who appeared testy through most of his cross-examination and often interrupted Wood, said that he merely told police that if the Rice relative was the person chasing him, he had a gun.

Rice Sr. and Rice Jr. are both charged with first-degree murder. Rice Sr. is scheduled to be tried as soon as the Boone case is completed; Rice Jr. is scheduled to go to trial in April.

CAPTION: Keith Arnez Boone had been ordered confined to his home.

CAPTION: Dona Ferguson was killed in her home while hanging curtains.