Paul Leon Jordan, convicted in the brutal stabbing deaths of a 3-year-old girl and her baby sitter, was sentenced yesterday to 40 years to life moments after a federal prosecutor argued that Jordan should "suffer for the rest of his days" for "his unspeakable horror."

Jordan remained motionless and without expression as D.C. Superior Court Judge Eugene N. Hamilton pronounced the sentence. Jordan, 48, would become eligible for parole after serving a minimum of 40 years in prison.

Jordan was convicted last month of the Jan. 24, 1985, slaying of Crystin Fletcher, the only child of two District police officers, and her 56-year-old baby sitter, Cora Barnes. The slaying occurred at Barnes' Northwest house.

The month-long trial was unusually contentious and centered on Jordan's videotaped confession that his lawyers maintained was false and induced by an advanced state of alcohol withdrawal and unethical police interrogation methods.

In a highly emotional plea for the maximum sentence, Assistant U.S. Attorney Amy S. Berman described the "suffering Jordan has left in his wake" that included a "marriage that will never be the same."

Jordan also was sentenced to 15 years to life for armed robbery in connection with the slayings. That sentence will be served concurrently with the other.

Barnes was a mother of three who was stabbed 30 times "in her own home . . . in her own little sanctuary," Berman said.

She then spoke of Crystin, and the young girl's relatives began to cry quietly. Fletcher's grandfather, squeezing his eyes, removed his glasses and bowed his head. "That was the child Paul Jordan strangled with his own hands because she had the temerity to cry," Berman said.

During the trial, the jury viewed the videotaped confession, in which a trembling Jordan told homicide detectives that he "started cutting" Barnes, a neighbor, and stabbed the child because she "saw what was what, so I had to take care of it, too." In addition, Berman introduced testimony that Jordan confessed to killing Barnes and the child when the child interrupted their lovemaking and an argument ensued.

Defense attorney James McComas sat with his arm around Jordan's shoulders during most of the proceedings.

When he spoke, McComas reiterated his client's innocence and told the judge that Jordan planned to appeal his conviction.

The trial was marked by some of the hardest-fought battles over the admission of evidence in recent memory at Superior Court.

McComas and defense co-counsel Penny Marshall argued that Jordan had confessed to a crime he did not commit. Putting police interrogation tactics on trial, the two defense attorneys attempted to show, in the words of McComas, that Jordan, suffering from severe alcohol withdrawal, confessed after "eight hours of interrogation, lies, false promises, tricks and psychological coercion."

Following the sentencing, some of the detectives involved in the case, who had sat in the first row of the courtroom, later shook hands with and congratulated Cortez Fletcher, Crystin's father, who attended most of the proceedings.

Fletcher and his wife have separated since the slaying and the wife's father, John G. Hickman, said it was "too difficult" for his daughter to attend yesterday.