Kelsey Alexander, of the Colorado City Police Department, has led the investigation since it started late 2010.
Although authorities aren't revealing much about the status of the investigation, Alexander says there will, eventually, be answers.
13-year-old Dunn was last seen at the home of her mother, Billie Dunn, on December 27th, 2010. She was reported missing the next day.
Billie Dunn's live-in boyfriend, Shawn Adkins, was the last person to see Hailey before her disappearance. Just days afterward, he told KRBC he had no idea where she could have gone.
"I'm clueless," said Adkins in a January interview.
The case went national on January 3rd, when Nancy Grace featured the case on her show on the HLN network.
The Dunn case was featured on the show several more times in the following days, before it faded from the national spotlight.
Billie Dunn and Shawn Adkins took polygraphs on January 5th. According to Dunn, they both failed.
On January 14th, authorities announced that Adkins had been named a suspect in the case. To date, he's the only named suspect, although there are other "persons of interest", including Billie Dunn. Adkins maintains his innocence.
"I would never do nothing to that little girl. I love her with all my heart," Adkins told KRBC.
Across Mitchell County and beyond, volunteers devoted countless hours looking for the missing teen, but search after search yielded no clues.
The key players in this case have had their share of legal issues. Hailey's father, Clint Dunn, has been arrested multiple times on unrelated charges. Billie Dunn was arrested in March for drug possession and hindering apprehension.
Affidavits revealing that pornography was discovered in the home of Billie Dunn and Adkins' mother were released February 25th. Mitchell County Sheriff Patrick Toombs says the images include child porn and bestiality. To date, no charges related to these findings have been filed.
Billie Dunn and her attorney spoke to KRBC on May 5th.
"I wish people would look for my baby as hard as they look for me," said Dunn
Shortly after the interview, Billie Dunn moved to Austin, where it's believed she is living with Shawn Adkins.