The trail of blood from the three Mexican children whose throats were slashed last year in a Northwest Baltimore apartment leads to two pairs of blue jeans worn by the relatives who are on trial for the murders, a prosecutor said in opening statements yesterday.

"Follow the children's blood because it will lead you to their killers," Assistant State's Attorney Sharon R. Holback told jurors as she laid out the case against Policarpio Espinoza, 23, and his nephew, Adan Canela, 18. Her opening referenced DNA evidence but described no motive.

Defense attorneys countered that police wrongly zeroed in on their clients, whom they described as uneducated illegal immigrants, because of pressure to solve a triple murder that shocked residents of even crime-hardened Baltimore.

Espinoza's attorney named two other men affiliated with the family as suspects who they said were never investigated, while Canela's attorney blamed Espinoza - and his own client's father.

Three children, an 8-year-old girl, her 9-year-old brother and their 10-year-old male cousin, were beaten, strangled and slashed shortly after coming home from Cross Keys Elementary School on May 27 last year. Their necks were cut so deeply - sawed with a long meat-cutting knife - that they all were nearly decapitated.

In testimony yesterday, the age of one of the children, some names of the relatives and some details of the crime differed from earlier accounts.

Defense wounds on the children's hands and arms, Holback said, showed that "they fought for their little lives. This was not quick. This slaughter was brutal and slow."

Prosecutors called their first three witnesses yesterday. A neighbor testified that she saw the defendants acting strangely near the children's apartment two days before the crime. She also said she saw Alexis Espejo Quezada, the 10-year-old, alive at his doorway about 4:20 or 4:30 p.m. May 27. Their bodies were discovered by the parents shortly before 5 p.m.

The father of Ricardo Espinoza, 9, and Lucero Espinoza, 8, testified next. Ricardo Espinoza Perez spoke of cradling his dead daughter before police arrived at the Samester apartment complex on Park Heights Avenue in Fallstaff.

"I grabbed my daughter by her arms and crouched down next to her and hugged her and loved her," he said, speaking in Spanish that was translated for the jury.

Later, at police headquarters, detectives showed him a long, meat-cutting knife - his own, Ricardo testified. It was a gift he'd gotten while working in a restaurant in New York, he said, a knife used for only one thing: "cutting New York steak." He said he kept the dull, old knife under the kitchen sink in the apartment.

Ricardo - Policarpio Espinoza's brother and Canela's uncle - explained the complex network of relatives who illegally immigrated to Baltimore from a poor village in Veracruz, Mexico, over the past decade. Also testifying yesterday was Victor Espinoza Perez, Canela's father and the eldest brother of Policarpio and Ricardo. He will return to the witness stand on Monday.

Ricardo's testimony revealed that his life was enmeshed with Victor's - the family food trucks they operated together were in Victor's name, as was the lease on the Fallstaff apartment.

Holback was unusually aggressive in her questioning of the two brothers, yet she did not make it clear why they were called to testify.

In her opening, Holback told jurors that in addition to three counts of first-degree murder, Espinoza and Canela face conspiracy charges. They conspired with each other, she said, and with "persons unknown."

Ricardo's testimony portraying Victor as the family patriarch fell in line with what appears to be Canela's defense strategy that his own father was behind the murders.

In his opening statement, defense attorney James Rhodes said there was a flurry of cell phone calls the day of the murder among Policarpio, his brother Victor and Victor's wife, Guadalupe Juarez Hernadez.

Those calls, Rhodes said, stopped about 3 p.m. and resumed about 4:30 p.m. - the silence roughly coinciding with the time of the murders.

Rhodes suggested two possible motives for the killings. Under one theory, Victor was "interested in one of the mothers" of the dead children, Rhodes said. When Victor's wife found out, she instructed him to "go over and take care of it."

Another possible motive that Rhodes posited was what some detectives quietly talked about in the days after the murders. Rhodes said Victor was responsible for transporting illegal immigrants into the country, charging up to $2,500 per person. Perhaps he would want to "send a message," the lawyer said. He did not elaborate.

Rhodes also warned jurors not to lump the two defendants together. DNA evidence, he said, may match Policarpio but does match Canela.

Holback said the children's blood cuts a trail from their slain bodies to the meat-cutting knife police recovered in the rear window of the apartment, to the baseball bat police found in the apartment yard to two pairs of the defendants' blue jeans.

One bloody pair was in a bag inside the trunk of Policarpio's car, and it had what appear to be Canela's skin cells inside the pant legs, Holback said. Another bloody pair, she said, was found inside Policarpio's Baltimore County apartment with his skin cells on them.

And there was "the teeniest, tiniest drop of Lucero's blood" on one of the shoes that Policarpio wore when he returned to the crime scene to comfort his grieving relatives, Holback said.

Like Timothy M. Dixon, Policarpio's attorney, Rhodes hammered in his opening that prosecutors have stated no motive linked to their clients.

"The state wants you to believe that, for no apparent reason, this 17-year-old slaughtered kids," Rhodes said.

Dixon said in his opening that prosecutors wanted to overwhelm jurors with grief and anger. He told jurors that when he and his wife first learned of the horrendous crime, they told each other that they hoped police would catch the killers.

"Today," Dixon said, "I hope they still do."