The miles are piling up now - almost as fast as the wear and tear on the car Maggie Zingman is driving. The people she passes are beginning to recognize her, too, waving and giving her the thumbs-up sign in tribute to her effort and to the smiling photo of her daughter that's featured on the side of the vehicle that continues down America's dusty, open roads. Their brief acknowledgement makes her feel good, but her goal is singular: to catch her daughter's killer.

This grieving mother is hoping that crisscrossing the country in her Nissan Cube - wrapped purposely in eye-catching purple and bearing that photo of her loving daughter - will help raise awareness about the decade-long case and ultimately put a brutal rapist and murderer behind bars.

Zingman is no longer a stranger to the road. Since beginning her journey seven years ago she has logged 108,000 miles through 46 states. She has driven from Tulsa to Dallas, from Shreveport to Albany searching for justice.

"A parent losing a child births a cavern inside her heart that seems like it will implode at any second," she says. "Passing out flyers on street corners helped in the first year, but I knew I needed to do more. So I hit the road. I needed justice for Brittany."

She calls her mission "Caravan to Catch a Killer."

THE MURDER

Brittany Phillips was just 18 years old in 2004 when she attended Tulsa Community College. She was a good student with a smile that lit up campus, and she had recently moved back to Oklahoma from Florida because her mother was worried about her safety since she was so far from home.

When she stopped showing up for classes, a friend went to her Tulsa apartment to check on her. What she found shocked her: Brittany's decomposing body lay in a pool of blood on her bedroom floor. She had been raped, suffocated and killed. The last of these observations was frighteningly clear. Later, cops would describe it as the most brutal kind of a murder - an indication that it was all very personal for the attacker.

Just four days before, on the evening of Sept. 27, Zingman had spoken to her daughter by phone. It was a casual conversation, like so many between a mother and a daughter. This time it was to assure her that she would help her find her an allergy doctor.

"I told her I loved her. She told me she loved me. We hung up. I never knew that would be the last time I would hear her voice," Zingman says.

Police believe that sometime that evening or during the early morning hours of Sept. 28 that followed, someone terrorized Brittany and murdered her. It was most likely the case that he was invited in. There were no signs of forced entry into her apartment, leading investigators to believe someone was either already inside Brittany's apartment when she returned home or had entered through windows or perhaps the French doors on the second story porch.
Brittany's friend made her nightmare discovery just 72 hours later on the day that would have been Brittany's 19th birthday.

The police investigation immediately turned to Brittany's inner circle, as is procedural in murder cases. Cops questioned a guy she had recently started dating. Then, while waiting for DNA test results, they questioned two brothers who had been interested in Brittany and had also lived nearby. The DNA did not match any of these suspects but detectives were already following a promising new lead. A security guard who had worked at the complex had been interested in developing a romantic relationship with Brittany, but she had blocked him from her phone and email accounts. Police noted that he had also acted a little too "interested" in the investigation. But his DNA did not match what was found at the scene and cops were eventually able to clear him.

Over the last decade, investigators have compared the crime scene DNA to more than 3,000 regional suspects and at least one million individuals cataloged in a federal database. The killer has eluded them so far. Not a single match - but Zingman is making sure her daughter's case never goes cold.

"I will never stop. From the moment she was murdered I said to myself that I would never stop," she says. "In many ways I am just beginning."

THE CARAVAN

Zingman's cross-country journey began in a Toyota RAV4 that eventually died after 300,000 miles and two rebuilt engines. For her latest trip she's driving a 2009 Nissan Cube that she's already put 192,200 miles on.

The stories she has accumulated along the way are as broad as they are deep. Ironically, they illustrate the best of America and stand in stark contrast to the worst of it that claimed her daughter and eventually marked the start of Zingman's lonely and frustrating journey. There's the Vermont family who flagged her down as she rode down a mountainside during a blizzard to give her money because they were so moved by her dedication. There's the Phoenix bus driver who stopped at a light and opened the vehicle's doors to reveal dozens of riders who were standing and clapping in tribute to her. Then there's the meeting she had in Virginia with Morgan Harrington's family. Morgan was a college student who was also murdered, and her case remains unsolved. In Gainesville, she parked next to an immigrant woman from Guatemala who had lost her family and friends to murder there. The woman's passion and compassion reminded Maggie of the way she had been in the beginning.

In addition to her primary mission to find justice for Brittany, Zingman's secondary goal is to push for legislation in all 50 states mandating that - just like submitting to fingerprinting - all offenders must submit to DNA sampling upon arrest. At present, two dozen states have some sort of DNA collection policy, but the laws are not uniform throughout the country and many states do not collect DNA from arrestees.

"I want to educate communities about how DNA saves lives. I can never get Brittany back, but maybe I can save lives," Zingman says. "I love my daughter so much. I just need some help."

'I'LL NEVER STOP'

HNGN has recently learned that law enforcement sources are following solid leads into Mexico to try and track down the person who killed Brittany. They believe the perpetrator has committed other crimes despite the fact there have been no DNA matches. Detectives have recently gone back through the roster of people who lived at Brittany's apartment complex (including their relatives) at the time of her murder. Their investigation has even taken them to the West Coast - to a man who admitted killing someone in Tulsa. That lead turned out to be bogus, but at least the case remains open and leads are being followed up on a weekly basis.

Despite such progress, Maggie Zingman is growing tired. One of the first detectives assigned to the case has retired, and she is also having trouble raising money for a reward fund. She also feels that the media isn't paying enough attention to her or her plan for important, life-saving legislation.

"If you're not famous or the murder isn't bizarre enough, no one cares," she says from the road that is her home away from home. "I have thought of giving up, but I won't. I will never stop."

She's commemorating the decade marking her daughter's death on a familiar path: a stretch of highway leading from Baton Rouge to New York City. After that, she'll head home to Tulsa, continuing to hope for a real break - any break at all - in her daughter's murder.

IMPORTANT! HELP MAGGIE ZINGMAN FIND BRITTANY PHILLIPS' KILLER

If you have any information regarding the murder of Brittany Phillips, please call the Tulsa Homicide Hotline at (918) 798-8477 or email crimestoppers@cityoftulsa.org

Jon Leiberman is an Emmy award-winning investigative correspondent, host, producer, victim advocate and author. He recently wrote the book "Whitey On Trial," about the mob. In addition to contributing to HNGN, he is a contributor to "Snapped" on Oxygen and various other television shows. Leiberman is a former correspondent for "America's Most Wanted." Follow him on Twitter @reporterjon.