How tree DNA helped police close in on a young mother's killer

On March 25, 2021, the body of 28-year-old Mengqi Ji was found buried in a shallow grave in Rock Bridge Memorial State Park near Columbia, Missouri. Above Mengqi's burial site was a juniper tree that would eventually tell investigators who left her lifeless body buried there.

"48 Hours'" correspondent Peter Van Sant reports on the case in, "The Tree That Helped Solve a Murder" airing Saturday, December 10 at 10/9c on CBS and streaming on Paramount +.

For over a year, Mengqi's husband Joe Elledge, then 23, had been insisting that his wife took only her purse and disappeared sometime in the early morning hours of Oct. 8, 2019. "We didn't have any big fights," Elledge told detectives, "I think the last big fight was actually the week before. And it wasn't really a big fight."

In an interview with CBS affiliate KRCG, Elledge said he suspected that his wife had left him and their 1-year-old daughter for another man. "I know she was talking to somebody else on the side." He said, "And I -— I didn't know that until after she had left. But — I — you know—whatever — whatever she's doin' — I just hope she's safe."

Then-Boone County prosecuting attorney, Dan Knight, told Van Sant that even early on, he had doubts about Elledge's story. Mengqi had left behind her passport, cellphone, house keys and car — but most importantly, she left behind her 1-year-old daughter. Knight told Van Sant "It became apparent early on that Mengqi would not have abandoned her child … She was a great mother." There was also no evidence that the young mother had run away. No Uber rides, airline tickets or credit card activity were ever discovered by investigators.

Sixteen days after his wife vanished, Joe Elledge was arrested, but not on charges related to his wife's disappearance. Dan Knight charged Elledge with child abuse, stemming from a photograph taken by his wife before she went missing, and sent to her mother in China. It was a picture of their baby's bruised buttock. Mengqi had told her mother that Elledge pinched the infant when she would not stop crying.

The day he was arrested, Elledge's apartment was searched, and among other crucial evidence in the disappearance of his wife, police seized a muddy pair of Elledge's boots. "Just in case, down the road, they might be relevant?" Van Sant asked Knight. "Something was amiss, yes … They sensed it."  

Knight also sensed something, and without having Mengqi Ji's body, he made a bold move. Based on evidence he showed to Van Sant in this week's "48 Hours" report, Knight charged Joe Elledge with first-degree murder. Charges were filed on Feb. 19, 2020 — just days before the United States began bracing itself for the global pandemic. "Then COVID basically shut down the court system," Knight told Van Sant.

Elledge had been sitting in jail on a $500,000 bond for about a year, when on March 25, 2021, a hiker in Rock Bridge Memorial State Park went off the beaten path and noticed a shiny object in the woods. As he got closer, Steven Roberts realized he had spotted a woman's purse. Then, using his walking stick to poke around, Roberts unearthed a skull and called police. A coroner would later determine that Steven Roberts had discovered Mengqi Ji's remains.

Remembering Joseph Elledge's muddy boots, Knight started researching cases that had used soil and gravel evidence to place people at the scene of a crime, and realized he had something even better — tree needles. With one call to a lab at the Missouri Botanical Garden, Knight set in motion the DNA testing of several juniper tree needles found stuck to the soles of Elledge's boots.

"Plants have DNA just like people?" Van Sant asked the garden's plant geneticist Christine Edwards. "Absolutely," she answered, "Every living organism in the planet has DNA."

After carefully removing the needles stuck to the bottom of Elledge's boots and extracting their DNA, Edwards' coworker, Alex Linan, was assigned to climb several juniper trees surrounding Mengji's grave. He meticulously numbered each tree and then scaled them one by one, picking fresh needles from the highest branches. Linan joined Van Sant at the gravesite to explain: "This involved a ladder and a 10, 15-foot-long pole pruner so that we could make sure that the needles that we were getting came from the exact tree."

Back at the lab, DNA from the needles extracted from Joe Elledge's boots was compared to the DNA from needles gathered in the field, and there was an exact match to the tree that stands directly over Mengqi Ji's burial site. Peter Van Sant asked Christine Edwards what that moment was like for her. "Really exciting," she said, "I think I yelled, "We got him … He was actually there … No doubt in my mind. He was there."

"Who'd ever thought it?" said Knight, "DNA from these juniper trees helped solve this crime." To which Van Sant responded, "I've never heard of anything like this before in my entire career at 48 Hours." 

In:
• Missouri
• DNA
• Murder