The man, Chris Long, underwent a bone marrow transplant four years ago during a battle with acute myeloid leukemia. The disease prevented Long’s body from producing blood as it normally would, so he went on to receive a lifesaving bone marrow transplant from a German stranger.
Long, who is an IT worker in the Washoe County Sheriff’s Department in Reno, Nevada, recovered following the procedure that, three months later, replaced his unhealthy cells with the donor’s healthy blood-forming cells. As a result, Long’s blood contains the DNA of his German donor.
But what about the DNA elsewhere in Long’s body? Renee Romero, a colleague of Long who ran the Washoe County Sheriff’s Department forensics lab, was curious and urged her coworker to find out.
“We need to swab the heck out of you before you have this procedure to see how this DNA takes over your body,” Romero told Long.
As a result of Romero’s urging, Long had samples of DNA collected before the transplant. “I didn’t even know if I would live,” he said.
Additional samples from numerous parts of his body were collected afterwards.
In some areas of his body, Long’s DNA as well as the donor’s were both found. Such was the case in swabs from Long’s lips, cheek, and tongue. Samples of his hair showed only Long’s DNA.
What the forensic team didn’t expect to find, however, was that four years after the bone marrow transplant, samples of Long’s semen showed only the German donor’s DNA. “I thought that it was pretty incredible that I can disappear and someone else can appear,” Long told the Times.
“We were kind of shocked that Chris was no longer present at all,” Darby Stienmetz, a criminalist at the Washoe County Sheriff’s Department, said.
But according to the Times:
“Mr. Long had become a chimera, the technical term for the rare person with two sets of DNA. The word takes its name from a fire-breathing creature in Greek mythology composed of lion, goat and serpent parts. Doctors and forensic scientists have long known that certain medical procedures turn people into chimeras, but where exactly a donor’s DNA shows up—beyond blood—has rarely been studied with criminal applications in mind.”
While it has been known that recipients of bone marrow transplants can throw a wrench in typical forensic investigations of crime scenes, the expectation has long been that the donor’s DNA as well as that of the actual person they’re dealing with will both be present. But what Long is experiencing raises entirely new questions of the use of DNA evidence in court cases.
As the Times reports:
“The assumption among criminal investigators as they gather DNA evidence from a crime scene is that each victim and each perpetrator leaves behind a single identifying code—not two, including that of a fellow who is 10 years younger and lives thousands of miles away.”
It may seem unlikely, but it must be considered moving forward that the recipient of a bone marrow transplant, of which there tens of thousands each year, may be able to commit a crime and end up implicating their donor, even if that person lives 5,000 miles away.
And it turns out, this very thing has happened in the past. During a criminal investigation in 2004, officials in Alaska uploaded a DNA profile found in semen to the DNA database. While there was a match, it matched a man who was in prison at the time of the crime. As it turns out, the man had undergone a bone marrow transplant and the man’s brother was eventually convicted.
An employee of the Alaska State Scientific Crime Detection Laboratory in Anchorage familiar with the case, heard of another case involving a bone marrow transplant that caused confusion during the investigation. A sexual assault victim’s description of the attack was met with skepticism by investigators after a DNA analysis revealed there were two attackers, not one as she reported. In this case, the victim was the recipient of a bone marrow transplant and the second DNA profile was that of her donor.
And in 2008, a visiting research scholar at the University of North Texas Center for Human Identification was working on identifying a victim of a traffic accident in South Korea. Blood from the scene indicated that the victim was a female while the body appeared to belong to that of a male. Eventually, the victim’s DNA was confirmed in a kidney while the spleen and lungs both showed male and female DNA. The victim had been the recipient of a bone marrow transplant from his daughter.
Thankfully Long’s colleagues thought to ask the question and search for the answer. If it weren’t for their curiosity, this unusual situation may have gone under the radar for years. But now the case has caught the eye of DNA analysts all over the world, after the unexpected findings were presented an international forensic science conference in September.
But another question remains unanswered. What if Chris Long has a baby? Would he pass the German’s DNA along to his child or his own? In Long’s case we’ll likely never know as he previously underwent a vasectomy. But the question is indeed an important one.
However, according to three bone marrow transplant experts consulted by the Times, it should be impossible for such a procedure to result in the passing along of someone else’s DNA. At least one doctor posits that it might have something to do with Long having previously had a vasectomy. But, they plan to investigate further to find out.