The mother of the Columbia teen-ager charged in the stabbing death and robbery of a convenience store clerk last month told police shortly after her son's arrest that she believed he was persuaded by her ex-husband to hold up the store, according to court documents filed in the case.

Linda Rites, the mother of David Hartless, 17, said the youth was obsessed by her ex-husband Leo J. Rites, 40, a convicted felon, who plotted the robbery to help him pay off prison debts from a drug habit, said the documents filed in Howard County District Court by police to support charges against Leo Rites.

Rites said her son was "obsessed" with her former husband, sneaking away to visit him at the Maryland State Penitentiary in Baltimore, where he is serving a 30-year sentence for armed robbery, the documents said.

Late Wednesday, police charged Leo Rites with first-degree murder and conspiracy to commit armed robbery in connection with the Oct. 17 slaying of Angelica Velazco, 20, a cashier at the High's store in a busy shopping center in Columbia.

Hartless was indicted yesterday by a Howard County grand jury on charges of first-degree murder and armed robbery.

At a bail review hearing yesterday, a Howard County district judge ordered Leo Rites held without bond. Hartless is being held without bond in the Howard County jail.

Linda Rites declined to comment yesterday on her statement in the report. Arcangelo Tuminelli, a Baltimore attorney hired three days ago by Linda Rites, said he did not know about her statements to police.

"She had no knowledge of the crime," Tuminelli said. "You have to take the police statement at face value."

At the bail hearing yesterday, Leo J. Rites said he planned to represent himself in the case. Saying he was indigent, Leo Rites, a slight, bearded man, asked the court to order the prison warden to provide him with a typewriter, paper and envelopes to prepare his defense.

"I am a pauper with no money in my institutional account, and less than $10 in my commissary account," Rites said. In court documents, police alleged that Leo Rites urged Hartless to rob the store because he was heavily in debt to other inmates for drugs. Police said Leo Rites owed "several hundred dollars" in loans for drug purchases.

Velazco was found dead in a rear supply room of the store with stab wounds on her abdomen and arms and she was almost decapitated. Police alleged that Hartless waited on customers at the store with bloodied hands after the stabbing.

Police said the alleged planning of the robbery took place in late September.

A person police described as a witness quoted in documents filed in District Court said he knew Leo Rites and that he bragged of his control over his stepson. "David will do anything I tell him to," the witness said Leo Rites told him, according to the documents.

In late September, the witness told police, he overheard a telephone conversation in which the two men plotted the robbery, the documents said.

According to the witness, Rites told Hartless to "find a small store where only one person was working, either an old person or a very young person." Rites suggested, the witness was quoted as saying, that Hartless use a knife he had given him as a Christmas present last year.

No murder weapon has been found, police said yesterday. Police sources have alleged that Hartless stabbed the clerk with a knife missing from a cutlery set owned by the family with whom he was living.

In a letter dated two weeks before the robbery, Hartless wrote to his stepfather that he planned to rob a store if the opportunity arose, the court documents said.

"Now as far as High's is concerned, I've gone in there every day and an opportunity never arises, but I'll keep trying until I do succeed, O'kay?" Hartless wrote, according to the court documents.

The letter, which was never mailed, also said Hartless was considering an alternate scheme to rob the home of "some rich people," but wanted to know where to sell stolen jewelry.

Leo Rites, who has a criminal record dating to 1964, last worked at The Bagel Shoppe in the Wilde Lake Village Green in Columbia, the same complex where the High's robbery occurred.

Steve Girard, the shop's owner said that when Leo Rites applied for a job as a baker he did not mention his criminal history, which includes two armed robbery convictions and forgery charges, according to a state prosecutor.

Girard said Rites was a good, dependable worker who showed up on time. "He did a reasonably good job," Girard said. "He was very, very quiet. He kept to himself."