Cause of death? CT scans shed new light in forensic probes

Administratively speaking, for each one of us, just a few terse words will tell the end of our story. The lines on a death certificate that describe cause and manner of death call for stark, dispassionate language that nonetheless can bring peace and closure to grieving survivors.  

This is especially true when a death is sudden, unexpected or unnatural. Such circumstances invite the involvement of someone like Dr. J. Matthew Lacy, chief medical examiner for King County, Washington. Trained as a pathologist, Lacy has conducted forensic death investigations for two decades, long enough to recognize a shift looming in the mostly unchanging field.  

“It's an exciting new tool to augment our understanding of what goes on in injuries and diseases that cause death,” Lacy said of a CT scanner that came online this summer at his Seattle office. The machine is part of a fledgling program to buttress his team’s methodical inquiries with CT scan interpretations from UW Medicine radiologists.  

The joint effort promises multiple upsides, not the least of which are better speed and clarity in providing information to decedents’ families.  

In an edited Q&A below, Lacy and Dr. Jonathan Medverd, chief of radiology at Harborview Medical Center, talk about death investigations and the emerging rationale for greater CT use locally and nationally. 

Q: Roughly what portion of deaths require investigation nationally and in King County? 

Lacy: Nationally anywhere from 10% to 20% of deaths should be looked at more closely. Every jurisdiction can have different laws or reasons for involving a coroner or medical examiner. In King County, there are roughly 17,000 to 18,000 deaths a year and probably 2,000 are investigated by our office.  

Q: Are there similarities among those deaths?  

Lacy: Most commonly, there’s a suspicion that a death is unnatural, like an accidental death. Drug overdoses are common scenarios. A lot of people these days die alone, and without medical care, so we don't know the cause in those cases. There is also the aspect of potential criminal liability.   

Q: What has traditionally been the role of CT scans in death investigations, and how does the new program change that?  

Lacy: My first exposure to postmortem CT was from the Armed Forces Medical Examiner in presentations more than a decade ago. They have a very sophisticated facility in Dover (Delaware) that examines military casualties. From CTs they learned a lot about how people were dying in combat in the Gulf Wars and also how to prevent or reduce some of those injuries.   

But our office didn’t start using CT until three years ago as part of this program, and it was just select cases at that time. Now that we have access to our own scanner, more than 90% of our cases are getting scanned.   

Q: What’s the advantage of using CT in death investigations?  

Medverd: We can see bones better with CT, and it differentiates soft tissues very well, too. The first case in our program was a bicyclist who had been hit by a car. CT showed that their body cavities had filled with blood because of injuries, and we predicted which tissues were fatally involved. My interpretation was a ruptured thoracic aorta, and when the decedent did go on to autopsy, it validated that prediction.  

In situations where the manner is not confusing or suspicious, we can now avoid autopsy because, through experience, we are getting better at recognizing the predominant cause with CT. 

There is also the consideration that some families’ cultural and religious beliefs preclude autopsying the body. CT readings may offer information to meet those families’ needs. 

Lacy: Pelvic fractures are also very difficult to fully describe with autopsy, but it's easy with CT to see those. For a collapsed lung, which might result from an injury to the chest, the autopsy detection of that hasn’t changed much in a hundred years: Water is placed in a tissue pocket and the space around the lung is incised through the water to reveal bubbles. But otherwise, we can’t see it because it’s just air. So if we don’t detect it, once we start opening the body, we’ve introduced our own air and that finding is lost.  

CT, on the other hand, shows air beautifully. It helps us forensic pathologists make more informed decisions about whether a person was alive when they suffered an injury, both for criminal and noncriminal cases.  

It’s also a fact that the double whammy of COVID and fentanyl has made us understand that we cannot do autopsies on every body that would have gotten an autopsy 10 years ago. We no longer have that option. So there has to be some other thing. 

Q: Who reads and interprets the CT scans? 

Lacy: We are grateful that UW Medicine faculty radiologists offer interpretations on a volunteer basis and on their personal time. Our pathologists are still looking at a lot of scans, too, and learning the software and how to use the machine. There's a learning curve. I think that we will start seeing the efficiencies a few more months down the road. 

Q: What value does the new CT scanner offer? 

Lacy: It’s mostly the possibility of how this technology will help us leverage our workforce, because we have to continue to respond to fluctuating workloads in a timely way. Having our own scanner, instead of having to schedule scans around clinical CT use over at Harborview, improves our team’s workflow.  

Medverd: It also resolves operational bottlenecks at Harborview, when we were sharing our clinical scanner and continually adjusting machine protocols. With clinical scans, patients have to get the lowest possible dose of radiation — which of course is very different from postmortem scans, where power levels can be much higher to get better images of bodies that are no longer at risk for radiation-induced injury.  

Q: Does this program have upside for radiology at UW Medicine? 

Medverd: We’re hoping to make a business model out of this relationship between our academic department and the King County Medical Examiner, and potentially offer forensic CT interpretation to other jurisdictions in Washington state and maybe beyond. There is a national shortage of forensic pathologists that such a service could help address. 

We're experts in imaging science and Dr. Lacy and his team are experts in forensic science. I think we're discovering that joining the best of both worlds is, in a way, making one plus one equal more than two.  

Q: What else? 

Lacy: Forensic pathology does not move very quickly. I think this is one of those times that we'll see the entire industry really change, with the integration of CT. It could be standard practice in 10 years. 

Editor’s note: A paper published this month in the Journal of Computer Assisted Tomography details the joint effort described above. The lead author is Kalpana Kanal, professor of radiology and architect of the forensic CT program at the University of Washington School of Medicine.  

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