In the realm of human sorrows, there is no more searing grief than that of parents burying a beloved child, and to lower a son into his grave just as he's flown from the nest is perhaps even more agonizing.

When a child is murdered, a different kind of anguish takes over. Parents need to know not only who but why, to know that no stone will be left unturned in the search for the killer.

Television shows like Law & Order and CSI tap deep into this psychological need. They show investigators painstakingly going over crime scenes, using tweezers to examine minute evidence, chemicals to sniff out blood and microscopes to peer into invisible places. With high-tech crime-solving, a bit of fabric or a ripped fingernail could put whoever is responsible behind bars.

That's what Jerry and Diana Gutheinz of Richardson believed when their 22-year-old son Brent, a senior living in student apartments at the University of Texas at Dallas, was slain in 1997.

He was their gorgeous middle son: sparkling blue eyes, blond curls and a sculpted body. A 1993 graduate of Plano Senior High, Brent adored girls, and they adored him.

When Brent disappeared on June 19, 1997, his boss guessed that he'd eloped with his former fiancee. Their volatile relationship had been off and on for weeks. They'd talked of getting married in Las Vegas on her birthday, June 22.

But as the days passed, his absence became sinister. At 11:30 a.m. on Sunday, June 22, a fisherman found Brent Alan Gutheinz's body on the banks of Squirrel Creek, in a rural area between Van Alstyne and Sherman in Grayson County. The body had been burned and mutilated: Brent's lower jaw had been removed and was missing, as were his upper teeth, his spleen and one kidney. His body had been doused with a solvent and set ablaze.

The Gutheinzes knew none of that when they learned a Texas Ranger had been assigned to investigate.

Wearing a Stetson, starched white shirt, pressed slacks and a star-shaped badge, Ranger Tony Bennie seemed the epitome of the dogged lawman. Part of the Department of Public Safety, Texas Rangers are often asked by county sheriffs to investigate homicides in rural areas. When Bennie sat in the couple's living room and quietly pledged to find whoever was responsible, the Gutheinzes felt reassured.

But with the approach of the seventh anniversary of Brent's disappearance, the Gutheinzes are no closer to learning who killed their son. Was the murder of Brent Gutheinz a mob hit, a drug deal gone wrong, an American Indian revenge ritual? The murder had elements of all these.

Unsolved murders are far from rare. But the Gutheinzes have come to believe that from the very beginning of the investigation Ranger Bennie and Grayson County authorities bungled the crime scene investigation--an allegation that is supported by the autopsy report and other documents from the Dallas medical examiner--and then failed to follow up on testing evidence and questioning possible witnesses and suspects.

Former Judge Robert Moss, retained several years after the murder to help the Gutheinzes get some answers, believes the Rangers have refused to disclose information to conceal what happened.

"Jerry's convinced there's a cover-up, and I'm convinced there's a cover-up, but for different reasons," Moss says. "Jerry's feeling was that someone in power got to them. My feeling was there was a cover-up to hide the sloppy work."

"I know Jerry might have called more than he should have, but he wanted answers, and they weren't giving him any," says private investigator Jerry Davis, a former Dallas police officer hired by the Gutheinzes after Brent's disappearance. "In my opinion, they botched it from the word go."

The oldest state law enforcement organization in North America, the Texas Rangers investigate everything from public corruption to mass murder. The legend of the Texas Rangers doesn't rest on crime-solving genius but on sheer tenacity, a philosophy encapsulated in this 100-year-old Ranger motto: "No man in the wrong can stand up against a fellow that's in the right and keeps on a-coming."

To be considered for a post as one of the 118 currently commissioned Rangers, an applicant must spend eight years with a law enforcement agency, and at least four of those must be with the DPS. Once chosen, Rangers go to work immediately, receiving ongoing training in criminal investigations and procedure. The amount of experience Rangers get in handling homicides depends on where they are posted. Many Rangers will investigate far fewer murders per year than a homicide detective in a medium-size city.

The public sometimes regards the Texas Rangers as a Texas version of the FBI. Not quite. The FBI requires agents to have college degrees; the Rangers require 90 semester hours of college, though three years of military or law enforcement experience can be substituted for that. But both the FBI and the Texas Rangers have the same attitude toward sharing information: They don't like it.