In the woods outside Huntsville, Texas, scientists are trying to
determine whether they can use the microbes that live on the human body
as microscopic witnesses that could help catch criminals.
It's a strange scene at the . At first, it's easy to miss the human bodies scattered among the tall pines, wild grass and weeds.
Katie Hayes Luke for NPR
Jessica Metcalf, a microbial ecologist at the
University of Colorado, says the mapping of changes in bacteria on
human remains at the facility in southeastern Texas "is really pushing
the envelope of microbial forensic science."
"We hope microbes can tell crime scene investigators how long a person has been dead,"
of Sam Houston State University explains, as she leads a group of
researchers and visitors from NPR through a tall, chain-link fence
surrounding the facility and down a dusty path to her research plot.
Katie Hayes Luke for NPR
"We want to do this as respectfully as
possible," says Sibyl Bucheli, a forensic entomologist at Sam Houston
State University, who is now looking for patterns in the ways
communities of microbes change as bodies decay.
The facility is one of the few places where, in the interest of
developing new tools for forensic science, researchers can leave human
bodies out in the open to study what happens as the remains decompose.
is an entomologist who has spent years studying the ways insects on a
body can help pinpoint how long a murder victim has been dead. Knowing
how long it takes a particular species of fly to complete its life cycle
from egg to larva to pupa to winged insect, for example, can help an
investigator figure out how long a corpse has been exposed to the
insects, establishing a minimum time since death.
Bucheli thinking. "If insects change through time, then so do bacteria,"
she says. "And if insects can be used, so can the bacteria."
possible, she says, that information from bacteria could improve the
accuracy of these time-of-death estimates. The microbes might also be
useful when insects aren't present, she says, helping to determine how
long a person has been dead, when insects aren't available to do that.
research is just in the beginning stages, but already, a scientific
team at the University of Colorado has been able to use bacteria alone
to narrow down how long a mouse has been dead to within three days.
"We're really pushing the envelope of microbial forensic science," says microbial ecologist f, a member of that Colorado team. She and her boss, microbiome researcher , have come to the forensics facility in southeastern Texas to collaborate with Bucheli, hoping to do with human bodies .
of the first tasks the day we visit is placing three fresh bodies in
the woods. A small tractor pulls up, carrying the first body inside a
blue plastic body bag. Three men lift the body off the tractor and place
it on the ground. They unzip the bag and carefully unwrap the white
sheet that swaddles the cadaver.
"We want to do this as respectfully as possible," Bucheli says.
a difficult moment. Corpses that have been in the field a little longer
look like mummies, barely recognizable as human. The new remains are
from people who have only recently died and donated their bodies for
scientific research. Bucheli is clearly moved. She pauses briefly for
what she calls her "thank-you moment."
"I'm deeply appreciative of the people who make my research possible ... all of them," she says.
scientists mark each body's position with a metal post and then begin
several hours of intense work, meticulously gathering dozens of samples
They carefully scrape the skin in the same spots
on each body and methodically scoop up dirt from precise locations near
the remains. Their plan is to come back day after day, month after
month, to sample these exact spots, to figure out if, over time, the
communities of bacteria in these various spots change in predictable
ways as time passes and the remains decompose.
for a microbial clock," Metcalf says. A clock like that could be used as
a reference tool in forensic investigations.
one day help police in other ways, too, the scientists say. The
population of bacteria on a person who died of natural causes, for
example, might look different than the bacteria on someone who was
beaten to death.
And because different varieties of microbes
are found in different places, the bacterial census of a corpse might
show whether a body has been killed in one place and then dumped in
another. Microbes might also help police who are searching for unmarked
"If you suspected that there's a body buried in a
certain field, can you just swab little bits of soil and say, 'Oh this
particular area has microbial organisms that we usually find associated
with a decomposing corpse?' " Metcalf asks. That's the sort of question
she and Bucheli hope their work will help answer.
not all. Knight says he thinks microbes could one day provide for each
of us a kind of microbial fingerprint that could help police solve all
sorts of crimes while we're alive, as well as after we're dead.
on campus, Knight demonstrates how it works. He pops open a small
plastic vial, grabs a cotton swab and pulls out his laptop to test the
Katie Hayes Luke for NPR
Already, Rob Knight, a microbiome researcher
at the University of Colorado, has been able to use bacterial samples to
link people to objects they've touched. One day, Knight says, a
"microbial fingerprint" might prove useful in linking a suspect to a
murder weapon or crime scene.
"You dip the Q-tip in the saline solution and you rub it
thoroughly on the individual key," he explains. The swab quickly turns a
"So what's on there is a combination of finger
grease, dust and bacteria ... maybe as many as a billion," Knight says.
"Definitely enough to track it back to an individual."
has been able to use an analysis of these communities of bacteria to
match people to objects they've touched. So microbes might be able to do
things like link a suspect to a murder weapon or the scene of the
crime, he says.
"There are a lot of cases where it's clear that
the suspect touched something but you don't have a print you can use
off it," Knight says.
He even thinks that analyzing the
different communities of microbes on peoples' bodies might eventually
prove to be a useful tool for tracking an individual's movements — to
see if the person had recently returned from Afghanistan or been in
Boston, for example.
All of this, Bucheli hopes, will one day
help answer the most important question for the families of victims: Who
"I'm somebody's mom," Bucheli says. "I'm somebody's sister. You always think about: Who? Who did this?"
no one yet knows how much of this research will prove useful in
forensics. Most practical applications are likely years away. But it's
already clear that some of these techniques will likely raise lots of
questions — about privacy, civil liberties and how much we want our
microbes to reveal about ourselves.