"Someone who knows something needs to come forward," says Jenny Carrieri, who thinks "someone knows more" about her twin sister's murder "than they're letting on"
Credit: Courtesy Jenny Carrieri

For 20 years, a single burning question has haunted Jenny Carrieri’s days and nights: Who killed her twin sister Joanne “Jody” LeCornu on a snowy Maryland morning back in 1996, and why did they do it?

And for 20 years, Carrieri’s desperate quest for the truth – no matter how horrific it may be – has done little more than leave her feeling confused and utterly vexed.

“It has been so frustrating,” Carrieri confides to PEOPLE during an interview about her sister’s cold case. “Since her murder, there have been so many stories and so many theories. I can’t sleep some nights because it hurts so much knowing that the person who took her from us is still walking around.”

Detectives for the Baltimore County Police Department’s Homicide Unit continue to investigate the case, and are hoping to provide the grieving sister with some solace soon.

This spring, the department renewed its efforts to bring Joanne’s killer to justice. They have released never-before-seen crime scene photos they hope will inspire someone who knows something to come forward.

One picture shows how the bullet broke Jody’s car window, went through the driver’s seat, and into her back.

LeCornu, who was a Towson University student at the time of her death, was discovered dead in her white Honda Civic, which was parked not far from her home in the Mount Washington section of Baltimore.

Police can’t say with absolute certainty that LeCornu knew her killer, who they believe approached her car and spoke with her for a bit before firing a single shot into her back.

LeCornu tried to escape her killer by driving across the street to the parking lot where her body would be found hours later, according to investigators.

But witnesses told detectives they saw an African-American man follow her across the street. He reached in through the driver’s side window, which was already rolled down, and shut the car off before taking something from the vehicle.

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The suspect then left the area in a white BMW, police tell PEOPLE.

“They have had a couple of suspects over the years, but never arrested anyone,” says Carrieri, sighing in frustration. “One of the scenarios they were floating for a while was that she was buying drugs, but there were no drugs in her system.”

LeCornu had completed a cocaine treatment program as a teen, Carrieri admits. But as an adult, her twin sister was fully committed to living a sober life, Carrieri says.

Another theory suggests LeCornu’s death resulted from an attempted robbery gone bad. Carrieri isn’t so sure.

“The police claim she was told by her boyfriend not to come home, and so that’s why she was sitting in her car when she was shot,” Carrieri explains. “She was killed on my parent’s wedding anniversary. My sister’s death was always hard on my father, who passed away without ever knowing the truth about her murder.”

While police have been unable to find a match for the two sets of fingerprints they lifted from LeCornu’s car, Carrieri says she’s optimistic revisiting the cold case will drum up new tips for investigators.

“Someone who knows something needs to come forward,” Carrieri tells PEOPLE. “There’s a $32,000 reward…there’s got to be someone or some people who know something. Someone knows more than they’re letting on.”

Det. Carroll Bollinger, a 30-year police veteran who joined the cold case unit more than 10 years ago and has been the lead on the LeCornu case, tells PEOPLE he thinks someone holds the key to solving this decades-old mystery.

“Relationships and associations change over the years,” Bollinger begins. “Maybe someone with pertinent information isn’t as close to the individual who committed this murder, and now, after 20 years, they’ll be willing to share what they’ve been keeping to themselves. That would be something we could work with.”

Bollinger tells PEOPLE investigators have re-entered the fingerprints they’d recovered from LeCornu’s car into the nation’s criminal database, hopeful they’ll get a hit after all these years.

He has also been conducting fresh interviews with several persons of interest who’ve been connected to the case. He’s also talking to LeCornu’s friends and ex-boyfriends again.

“We’re also trying to develop DNA off of some of the items we’d collected from the scene where previously, we couldn’t,” says Bollinger. “We are going over video taken at the time, using new technologies. Our video examiners are now able to take apart a video and retract an image from it where you couldn’t do that 20 years ago. We’re just going back to see if we can shake the tree and get any apples to fall.”

LeCornu’s murder also torments Bollinger, who says he’d like to close the case file before his eventual retirement.

“It’s a difficult place to be sometimes,” Bollinger acknowledges. “I’ve been talking to her family pretty regularly since she was killed, and I am looking for any clue that could provide her sister and mother with closure.”

Investigators ask that anyone with any information on LeCornu’s murder call the Metro Crime Stoppers tip line at (866) 7-LOCKUP.

“It’s hard feeling this hopeless and frustrated with the progress being made on her case,” says Carrieri, who recently hired a private investigator to look into her sister’s homicide. “I really don’t want to die without knowing what happened to her.”