Linking severed feet to missing persons a challenge, experts say
The disturbing discovery on Monday June 16 of the remains of a left foot in a running shoe in the water near Westham Island in Ladner, B.C., may not seem like much to go on for forensic investigators.
But the remains, one of five feet discovered in the last year and a half in the same region, could potentially contain deoxyribonucleic acid (DNA), bone minerals and trace evidence, forensic experts say, while the shoe itself might provide some history on the time and place when a person may have gone missing.
The difficulty, they say, is in turning such evidence into something that can identify an individual and help families looking for information on missing persons.
The problem was exacerbated by the news that a sixth shoe, found near Campbell River, contained a skeletonized animal paw packed with dry seaweed in what the B.C. Coroners Service called "a reprehensible hoax."
The discovery of the hoax highlights the first investigative tool at the disposal of the coroners service: a simple examination of the shoe and bones it contains.
Pathologists and anthropologists can better estimate everything from the height of the person to their age based on that study, B.C. chief coroner Terry Smith said.
But to glean more information, DNA evidence is often required.
The process of raising DNA profiles based on the remains can be a painstaking process, Smith told CBC News, but that's only the beginning of the work.
"The [DNA] profile itself really is nothing more than something which looks like a barcode, and it really means nothing until you have something to compare it to," he said.
"If we know that a given profile belongs to a particular person, then comparing the profile we raised from the found remains then allows us to make a definite match."
Finding that match isn't as easy, he said, because of the vast numbers of missing persons, not all of whom have DNA samples available for comparison.
Where did they come from?
The Strait of Georgia is a large, deep, inland basin that is strongly influenced by wind, tide and river discharge. It is 220 kilometres long and about 25 kilometres wide at its narrowest point.
More than 3,000 species of marine life — including seals, sea lions and orcas — live in the strait. Many of them are carnivores.
Water temperature in the strait ranges from about 7 C to 9 C, cold enough to slow the rate of a body's decomposition.
Susan Allen, an expert on ocean currents at the University of Victoria, says the body parts must have originated within B.C.
"In general, the water is flowing out of the strait, not into the strait," she told CBC News. "So you would expect floating objects to leave the strait, not enter the strait."
Allen said the body parts aren't necessarily popping up to the surface from the bottom of the strait. There are countless bays and hundreds of rivers — including the Fraser River — that flow into the strait.
She said the body parts could be coming from anywhere — except the waters west of B.C.
Dean Hildebrand, head of the forensics program at the British Columbia Institute of Technology, said the process of extracting DNA from a sample such as a human bone can take as little time as a week or two.
The process involves cleaning the sample to eliminate potential contaminants and then isolating a few cells to look for relatively clean DNA strands. These strands are then replicated in a laboratory to create larger samples to work from, so that even a DNA sample that has degraded over time can be turned into something usable for study, he said.
That replication process is particularly important given that the remains in these cases have been found near water, because moisture is — along with temperature — an important cause of genetic degradation.
Exposure to water
Exposure to water is also likely why the feet broke away from the rest of the body, said Lynne Bell, a forensics professor at Simon Fraser University.
Had these feet not been in shoes, the bones of the foot would likely have broken away from the rest of the body in the water, said Bell, who is not involved in the investigation. Human remains recovered in forests can also have a similar separation of shoe-clad foot from the rest of the body, although that process would take much longer, she said.
That the shoes were running shoes also meant they would float, she said, allowing them to travel downstream while the rest of the remains sank.
Bell said DNA is the best source of evidence for investigators attempting to link the remains to a person, because it can positively identify a single individual. However, there are other methods for getting more general information about a person, she said.
The shoes could be a source of potential information, she said, starting with the most basic information — the size and the brand of the footwear. While both could provide a potential match with an individual, the brand, if new enough, could help investigators figure out when the person might have gone missing.
More advanced study, such as examining to see whether pollen from trees and other plants has hitched a ride on the footwear, might provide information on a particular geographical region, she said.
Oxygen isotopes offer clues
Similarly, studying the minerals in the bone itself could provide a geographical marker of where a person might have lived, Bell said. She said the study of oxygen isotopes found in the bone could place a person at a certain latitude, as the oxygen value of drinking water changes depending on the location's distance from the equator.
"That would help narrow a missing person search, but it won't give you an address," she said.
As investigators work on the case, online comment boards have offered possible explanations on how the discovered remains may be linked.
Bell said investigators will likely call on water current experts to see whether the locations of the discoveries are linked, but she said she suspects the unusual appearance of five different feet in the same region over a short span of time makes it "highly plausible" they are.
"It could either be a known incident, such as a plane or boat crash, or it could be something we don't know about, such as a criminal incident," she said.
Bell said she feels confident investigators will eventually be able to solve the mystery, linking the remains with each other, but she said the greater challenge remains identifying whom the feet belong to.
"It's incredibly challenging from the forensic point of view, because even if we find the DNA, we don't know who these people are and why their remains are being recovered from the water," she said.