What Happens If You Donate Your Bone Marrow And The Recipient Commits A Crime?

What is bone marrow/stem cell donation – and who needs it?

Stem cells are a very nifty type of cell produced by bone marrow that can develop into many different cell types and have the potential to treat many diseases or repair damaged tissue.

“Stem cell donation is a lifesaving treatment for patients with blood cancers and blood disorders that involves replacing a patient’s blood stem cells and immune system with cells from a healthy donor,” Pat Smith, from Anthony Nolan (the world’s first stem cell register), told IFLScience. 

People living with these conditions will often be prescribed radiotherapy or chemotherapy treatments. Unfortunately, standard chemotherapy or radiotherapy sometimes isn’t enough to help treat a patient’s blood cancer. In some cases, a bone marrow transplant is the next treatment option. A bone marrow transplant aims to replace a patient’s cancerous blood cells and immune system with a fresh immune system that can fight any remaining cancer in the body, and help take the patient into remission.

There are two types of transplants: autologous and allogeneic. This fancy terminology basically means someone who uses their own stem cells (autologous), or someone who receives stem cells from a matching donor (allogeneic). For the latter, stem cells can be collected from the bone marrow directly (while someone is under anesthetic), or through the collection of blood.

In Europe, there are a high number of transplants from matching donors. For instance, in 2011, there were 14,549 allogeneic hematopoietic stem cell transplants and in 2014 there were 16,946. As more people are becoming aware of bone marrow transplants and more people sign up to the transplant register, this number will get higher and higher. 

Bone marrow donation and chimerism

There are weird things that can happen when people get a bone marrow donation. One person developed a kiwi fruit allergy, which is due to chimerism. 

While the word chimera comes from Greek mythology, where it describes a mythical creature comprised of various animal parts, in cases like this, chimerism is due to a patient having cells in their body that come from different genetic origins.

After bone marrow donation, the donated blood stem cells establish themselves in the recipient’s bone marrow and are put to work making new healthy blood cells. Chimerism is a side effect of bone marrow transplant, as the recipient will have a mixture of their own cells and the donor’s cells in their body. It is now known that donor cells can sometimes reside in many different tissues and this can lead to odd reactions. So, in the case of the man who became allergic to kiwi, the allergy was due to the donor’s hematopoietic stem cells.  

Chimerism is a very common consequence of bone marrow transplant. One study investigated 24 different recipients who had all had an allogeneic hematopoietic stem cell transplant. They detected donor chimerism in all of the recipient’s blood samples, with some people having donor-derived cells in other biological samples.  

Another intriguing discovery happened with a guy called Chris Long, who worked in a sheriff’s office and had received a bone marrow transplant. He and his colleagues saw an opportunity and conducted DNA analysis on Long. It was discovered that his donor’s DNA was present in various bodily samples, including semen. However, experts agreed that a donor’s blood cells should not be able to create sperm cells and this may have been a result of a previous vasectomy. 

With chimerism being such a common occurrence, is there any way that samples left at crime scenes by recipients of a bone marrow transplant could lead to the donor instead?

How often has this been a problem in forensics?

In criminal cases, forensic scientists often scour the scene for any biological samples (with blood being one of the most common sources) that can point them to the perpetrator. Over the last few decades, DNA analysis has been front and center of forensic investigations. Typically, a person possesses a unique DNA profile and this can be used to identify specific people. 

A few decades ago in Alaska, there was a serious sexual assault. DNA from semen that was collected from the victim matched a blood sample from a known criminal, so a potential suspect was quickly identified. Easy case, right? Well, one of the issues was that the supposed suspect had a very convincing alibi – he was already in jail when the assault took place.      

It turns out the jailed man and the suspect shared the same surname. After a bit of snooping, it was revealed that the inmate received a bone marrow transplant from his brother. This meant that his blood had cells that matched with his brother’s DNA profile.                                               

In another crime that occurred in 2000, a woman suspected she had been sexually assaulted while unconscious. At the time, many forensic samples were analyzed and the genetic profile they produced was compared to the United Kingdom’s National DNA Database. What was odd was that a mixture of different genetic profiles were found in the buccal mucosa (saliva) and this was also seen in blood and hair samples of the victim. It was discovered that she had undergone a bone marrow transplant when she was a child, with her brother being a donor, and this is what was contributing to the confusing genetic profiles – she was a chimera with a mixture of her own and her brother’s DNA.

In another devastating case, there were two corpses found after a house fire. Due to how bad the fire was, there were no distinctive features left that could be used to identify the people who were killed in the blaze. As such, investigators had to rely on genetic analysis to find out who they were. The first person was identified easily, the second, however, was a bit more difficult. This was because the second person had had a bone marrow transplant five years previously, and the samples collected showed alleles that belonged to the donor. Multiple tests had to be done to ensure that the person killed was who the authorities thought they were.  

Should we be worried?

So far it is clear that bone marrow transplants have sometimes led to confusing crime scene situations. However, that still begs the question: How concerned should people be about this happening? 

Well, this scenario is incredibly rare, and normally any sample found at a crime scene would be recognized as an unexpected mixture. 

In forensics, you can receive biological samples from multiple areas, such as:  

1. Named individuals (living victims and suspects) 
2. Deceased victims 
3. Evidence found at the scene 

“Named individuals generally [supply] mouth swabs which will have the person’s own DNA, rather than the donor DNA which is in the blood”, Denise Syndercombe Court, Professor of Forensic Genetics at King’s College London, told IFLScience. “Sometimes you can get some blood cells in the mouth swabs and that will appear as a mixture in the reference sample which will then be investigated.” 

In the event that the blood sample had 100 percent chimerism (only donor cells), then it’s possible that the forensics expert would only identify the donor’s DNA.

Pat Smith

For samples collected from deceased victims who have had a bone marrow transplant, there would be full or partial chimerism. In criminal cases, scientific investigators would rely on multiple body samples for identification (i.e. fingerprints, dental/bone records, blood, and tissue samples), so investigators would be quick to identify if there is a case of chimerism happening, which would trigger further investigations. 

“If the blood of a recipient of a stem cell transplant was found at the crime scene, a forensics expert would be able to distinguish two sets of DNA and identify the possibility of a stem cell transplant,” Smith explained.

“In the event that the blood sample had 100 percent chimerism (only donor cells), then it’s possible that the forensics expert would only identify the donor’s DNA. However, forensic analysis of any other tissue left at the crime scene (skin, hair, saliva) would have the recipient’s DNA – indicating the possibility of a stem cell transplant. The police would also need to have the donor’s DNA on file to trace a potential match.”

In all forensic investigations, there are always questions that the forensic expert asks suspects, relatives of suspects, and anyone remotely involved in the crime. This will provide critical clues as to whether the owner of the biological sample that is found at the scene has ever been involved in bone marrow donation. 

We aren’t aware of anything like this happening in medical history.

Pat Smith

One way to find this history is to simply “ask them – ask their relatives (as they may be the source of the donation),” Court added. “If [there is] unidentified blood, look for low-level mixtures that are reproducible in different blood stains, preferably on different items. If not blood, it is unlikely to be a problem.”

“It’s very difficult to imagine a scenario where a donor is incorrectly linked to a crime solely because of the presence of their DNA from donated stem cells at a crime scene, and we aren’t aware of anything like this happening in medical history”, Smith said. 

Should you still donate your bone marrow?

Despite these very rare cases, it is still important that people continue to donate bone marrow. 

“In our experience, the potential benefit to patients whose lives may be saved by a [bone marrow] transplant outweighs any worries from donors about the extremely unlikely event of having their DNA found at a crime scene,” Smith explained. “If you’re aged 16-30, you could be the answer a patient is looking for. Learn more about signing up to the stem cell register at anthonynolan.org.”

The chance of the events described above ever occurring is extremely rare. After scouring the internet, consulting numerous resources, and reaching out to experts, we were only able to find less than a handful of occasions, and all of these were easily solved. So, if you have the chance to sign up to register, we highly encourage you to do so. There are other stem cell registers depending on your location, such as DKMS and NMDP.