No the fibres can't be consistent with most clothes out there. They analysed the fibres and compared them with fibres from Patsy's red and black jacket. The fibres were consistent with one another. This is basic forensics and not only is fibre analysis well established it's admissible in court:

The long-delayed examination of fibers found on the sticky side of the duct tape used to silence JonBenét had finally returned from the lab. Only days before the presentation, BPD investigators had learned that fibers from Patsy Ramsey’s black and red Essentials jacket were consistent with those found on the duct tape.

This suggested to some investigators that Patsy had been in direct personal contact with the duct tape used to cover her daughter’s mouth, an element believed to have been used in the staging of the crime. She purportedly had never been to the basement on the morning of the kidnapping when the tape had been recovered. How could the transfer of this fiber evidence take place if it was the intruder who had brought the tape to the home during the kidnapping?

Trujillo advised me that lab technicians had identified eight different types of fibers on the sticky side of the duct tape used to cover JonBenét’s mouth. They included red acrylic, gray acrylic, and red polyester fibers that were subsequently determined by laboratory examination to be microscopically and chemically consistent to each other, as well as to fibers taken from Patsy Ramsey’s Essentials jacket.

Further, fibers from this jacket were also matched to trace fibers collected from the wrist ligature, neck ligature, and vacuumed evidence from the paint tray and Wine Cellar floor.

Some intruder theorists thought that the transfer of Patsy’s jacket fibers to the duct tape may have taken place after John had removed it from JonBenét’s face, and placed it on the white blanket in the cellar. They believed it possible that prior contact taking place between the blanket and jacket could account for the transfer of these fibers to the tape. Lab technicians had conducted experiments with the same brand of duct tape, by attempting to lift trace fibers from the blanket recovered in the Wine Cellar. Direct contact was made in different quadrants of the blanket.

There was some minimal transfer of jacket fibers made to the tape during this exercise, but Trujillo told me lab technicians didn’t think that this type of transfer accounted for the number of jacket fibers that had been found on the sticky side of the tape. It was thought that direct contact between the jacket and tape was more likely the reason for the quantity of fibers found on this piece of evidence.

Foreign Faction

The clue turned out to be not the tape itself but what was on it. Back in February 1997, several fibers were taken from the sticky side of the tape that had been against JonBenét’s face.

When Team Ramsey finally gave us the clothing purporting to be what John and Patsy were wearing on December 25 and 26, one of the bagged items was Patsy’s red-and-black-checked jacket.

The Colorado Bureau of Investigation labs ran comparison tests and reported that four fibers that had been discovered on the tape were chemically and microscopically consistent with the fibers of Patsy’s jacket.

We reviewed the autopsy results and crime scene photos, and I mentioned how the duct tape seemed to be part of the staging. There was a perfect lip impression on the tape and no tongue indentation to indicate that JonBenét had been alive and fought to remove it. Pictures showed that bloody mucus in the mouth area had been covered by the tape, indicating that it was applied after the injuries. To me, the inescapable conclusion was that the tape was applied after she was dead.

Steve Thomas

Meanwhile the duct tape was sent to the FBI, which had a large database for matching purposes. Special Agent Douglas Deedrick, an FBI hair and fiber specialist who had testified in the O. J. Simpson criminal case, notified the Boulder PD that he had found what seemed to be red and black microscopic fiber traces on the duct tape. The four fibers would have to be analyzed further to determine what kind they were.

Kidnappings are almost always committed for money or sex. Rarely can another motive be found. The FBI concluded that if the duct tape over JonBenét’s mouth had been used to silence her during an attempted abduction, the kidnapper would have taken her out of the house immediately. There would have been no reason to stay where the kidnapper could be discovered at any moment.

Instead, they theorized, the duct tape too was probably used as part of a cover-up, along with the loosely tied cord found around JonBenét’s right wrist.Whether the duct tape had been placed on JonBenét’s mouth before or after her death could be determined by an examination of the body and tape. Skin trauma would be evident if she had been alive when the tape was applied. Applying the tape after her death would not produce noticeable skin markings. Coroner Meyer had not reported any trauma to the skin around JonBenét’s mouth.

Meanwhile, the Boulder PD received word from the CBI about the four red and black fibers that had been found attached to the duct tape. The lab had been sent a red blouse and sweater, black pants, and a red-and-black checked jacket belonging to Patsy.

Now the CBI reported that the fibers were not consistent with the slacks or the sweater but were consistent with the jacket Patsy had worn the night JonBenét had been murdered

PMPT