One hundred days after 84-year-old Nancy Guthrie vanished from her Tucson home, the investigation's most promising lead, a DNA sample recovered from her property, remains under analysis at the FBI's crime lab. No credible suspects have been publicly identified. No arrest has been made. And the family of the "Today" show host Savannah Guthrie's mother is still waiting for answers.

The grim milestone arrived Monday with investigators no closer, at least publicly, to explaining what happened in the early hours of Feb. 1, when Nancy Guthrie is believed to have been taken from her Arizona residence. Law enforcement sources told CBS News that DNA testing was still in the works, a timeline that has frustrated observers but that forensic experts say reflects the painstaking reality of crime-lab science.

Pima County Sheriff Chris Nanos refused to discuss the evidence directly, telling reporters the case's integrity demanded silence.

"It would be highly inappropriate of me to speak to the evidence. We have to keep the integrity of this case. If we make an arrest, that individual has the right to a fair trial. I can't sit here and address all of that."

Nanos added a pledge: "We are working hard with all of our partners to resolve this case, and we will."

A winding forensic trail

The DNA sample's journey to the FBI lab was not a straight line. Pima County sheriff's detectives initially sent the evidence to a private lab in Florida. The FBI had offered early on to analyze the DNA at its own facility, but several weeks passed after Nancy's disappearance before the evidence was turned over to federal investigators.

That delay has drawn scrutiny. The Pima County sheriff has faced accusations of letting a personal grudge with the FBI derail the search, a tension that hangs over every development in the case. Whether the weeks-long detour through a private Florida lab cost investigators time that mattered remains an open question, one Nanos has not answered.

Authorities have not disclosed what type of DNA is being analyzed or precisely where in the home it was found.

What surveillance footage showed

The night police believe Nancy Guthrie was kidnapped, security footage captured a masked man loitering around her front doorstep. Blood spatters were later discovered on that same doorstep, physical evidence that pointed to violence.

Early in the investigation, the FBI recovered a black glove near the Guthrie residence, and that glove became a focal point. The FBI later said the glove, found about two miles from the home, contained DNA and appeared to match the gloves worn by the masked person in the surveillance video.

Preliminary results produced an unknown male DNA profile. The FBI stated it received those preliminary results and was awaiting quality control and official confirmation before entering the profile into CODIS, the national DNA database. Investigators collected roughly 16 gloves near the home, but the FBI said most were discarded searchers' gloves. The DNA-bearing glove was different.

Whether that CODIS search ultimately returned a match is a question the public record has not definitively resolved. Earlier reporting indicated CODIS returned no match on the glove DNA, a setback that may explain why the investigation has stretched to 100 days without a named suspect.

SWAT raids, detentions, and no arrests

The investigation has not been passive. The Washington Examiner reported that SWAT teams and federal agents executed a search warrant at a residence about two miles from Guthrie's home, with numerous law enforcement vehicles involved. The Pima County Sheriff's Department confirmed law enforcement activity near East Orange Grove Road and North First Avenue was related to the Guthrie case.

Reports indicated three people were detained for questioning during that operation. But the effort ended without arrests, and at least one cooperative man was released. Investigators also found DNA that did not belong to Nancy Guthrie on her property, along with gloves, all of which were sent for testing.

The case also produced ransom notes. TMZ cited an alleged note that told recipients to "be prepared to go international" to locate the "main individual" behind the abduction. Former FBI agents have said the kidnappers showed no concern for Guthrie's life and used the notes to torment the family, a chilling assessment that underscores the severity of what investigators are dealing with.

Why the FBI lab takes this long

Retired FBI special agent Jason Pack explained that DNA analysis, including the work of building out entire family trees to identify suspects, moves at a pace that bears no resemblance to television procedurals.

"That kind of work is slow because it has to be right."

Lance Leising, an ex-FBI special agent in Arizona, offered context on how the bureau prioritizes evidence. A strand of hair found somewhere in a house is one thing, he said. But a strand of hair near the victim's last known location, such as in her bed, "would be a high priority for the FBI."

The distinction matters. Without knowing where in the home the DNA was found, the public cannot gauge how central this particular sample is to identifying the person who took Nancy Guthrie. Authorities have kept that detail under wraps.

A family still waiting

Savannah Guthrie has made public appeals for her mother's return. In an Instagram post, she addressed whoever abducted her mother, or anyone who might know where she is being held.

"It is never too late to do the right thing."

Nancy Guthrie, 84, needs vital daily medicine, a fact that has added urgency to the search from the beginning. Every day the case remains unsolved is a day her health is at greater risk.

Pima County's sheriff has said investigators were closing in on answers, but the 100-day mark arrived without a public breakthrough. Nanos's assurance that "we will" resolve the case is a promise, not a result.

Open questions that demand answers

The Nancy Guthrie case sits at an uncomfortable intersection of high-profile attention and investigative opacity. Several questions remain unanswered. Why did Pima County detectives send the DNA to a private Florida lab before accepting the FBI's offer? What type of DNA is being analyzed, and where exactly in the home was it recovered? Have investigators developed any credible leads they have not disclosed publicly?

The FBI's early identification of the glove as a match to the suspect's suggested the investigation had momentum. That momentum, at least from the public's vantage point, has stalled.

Sheriff Nanos is right that a future defendant deserves a fair trial. But the public, and an 84-year-old woman's family, also deserves to know that every available resource was deployed without delay and without jurisdictional friction. The record so far raises doubts on that score.

A hundred days is a long time for an elderly woman who needs her medicine. It is not too long for accountability to catch up with whoever took her, but only if the people running the investigation got the basics right from the start.