'We know who killed her': PI blows the lid on mysterious 1994 killing of student, 19, and claims murderer will face charges 'imminently' - as she says he kept Mickey Mouse watch similar to the victim's in an eerie display cabinet

A private investigator who has dedicated a decade of her life to unmasking the killer of a 19-year-old Arkansas student believes the suspect is soon to face charges.

LaDonna Humphrey is an author and advocate based near the city of Fort Smith, where Melissa 'Missy' Witt grew up and was last seen alive.

The teen vanished on December 1, 1994, after going to surprise her mother at a bowling alley. Six weeks later, hunters discovered her naked body in the Ozark National Forest.

'We are very confident that we know who killed Melissa, which is a huge place to be,' Humphrey told the U.S. Sun.

The author has dedicated the past eight years of her life to scrutinizing the cold case in the hopes of preventing the teenager from becoming 'just another female victim.'

Melissa 'Missy' Witt, 19, vanished from the parking lot of a bowling alley in Fort Smith, Arkansas in December 1994

Her body was discovered by hunters in Ozark National Forest (pictured) six weeks later. She was naked and without her belongings

LaDonna Humphrey, an author and private investigator, has dedicated nearly a decade of her life to hunting Witt's killer - and believes the suspect will face charges 'imminently'

As a mother to five daughters herself, Humphrey feels personally responsible to find Witt's killer - and believes he will be charged 'imminently.'

On the day of her disappearance, the teen was planning to meet her mother after an argument but never made it inside the bowling alley.

Investigators found blood in the parking lot and apparent signs of a struggle.

An autopsy showed she had been strangled before she was dumped in the forest, around 45 miles from home. Her clothing and belongings were never found.

Humphrey has written several books about the decades-long cold case, and the third and final installment features interviews with members of law enforcement who investigated the case.

The book, which is out later this month, lays out three pieces of evidence Humphrey believes will lead to the identification of the real murderer.

For years, police held convicted killer and rapist, Larry Swearingen, as the prime suspect in Witt's case.

Swearingen had been found guilty of the 1998 murder of another 19-year-old, Melissa Trotter, in neighboring Texas.

He professed his innocence up to the day of his execution in August 2019, and Humphrey herself is convinced he was not involved in Witt's case.

Witt was strangled before her body was dumped in the woods. Police found blood and signs of a struggle in the parking lot from which she had vanished

Convicted killer Larry Swearingen was considered the prime suspect in Witt's case, but denied involvement up to the time of his execution. As Humphrey pored over Witt's journals, she found a promising lead

The author declined to name the suspect, but says he 'has a very violent history' including the abuse of a number of ex-girlfriends

As she launched a 'deep dive' into the teen's life that included combing through her diary, one suspect continued to crop up.

Humphrey has declined to name him amid the pending investigation, but shared he 'has a very violent history,' with nearly two dozen people coming forward 'to talk about the violence that they had experienced at his hands.'

This included ex-girlfriends who had been beaten and strangled by the suspect, Humphrey said.

A breakthrough came when she managed to trace the man's former roommate, who said the suspect was 'supposed to see Melissa the night she disappeared.'

He also had a Mickey Mouse watch that he displayed in their apartment, adding to the mystery. Witt was wearing a similar watch at the time of her death, but it was never recovered.

'He fits the profile given by the FBI of Melissa's killer,' Humphrey said of the suspect, adding that he had served prison time.

She conceded that there will be no way to prove the watch was Witt's 'until we get our hands on it,' but insists it was more than a coincidence.

Last December 1 marked the 29th anniversary of Witt's abduction from the Bowling World parking lot in Fort Smith.

The man's former roommate shared that he kept a Mickey Mouse watch on display in their apartment, similar to one Witt had been wearing that vanished from her body

Humphrey's organization, All the Lost Girls, partnered with Who Killed Missy Witt to put forth a $29,000 reward for 'critical pieces of information' connected to the case

Widespread fascination with the case has sparked the genesis of organizations specifically dedicated to hunting her killer.

Humphrey is the co-founder of All the Lost Girls, a nonprofit that offers support for female strangulation cold cases in the United States by funding services like DNA testing and genetic genealogy.

Her group partnered with another organization, Who Killed Missy Witt, to put forth a $29,000 reward for 'critical pieces of information' related to the case.

'This was a young girl who had her whole life ahead of her and somebody took it from her,' Witt told 5 News.

'And it left behind people who were devastated and have had to try to go on with their lives for 29 years without justice.'

The author and amateur sleuth once again expressed her belief that justice is around the corner. 

'I believe that we're gonna see it solved in the next year, I firmly believe that,' Humphrey said.

'I really am so encouraged that even after 29 years, people are saying we can't let this go on another year, we don't want to get to the 30th anniversary, we want answers now.'