If a body is found in a field, and the cops suspect foul play is involved, establishing
the exact time of death is critical.
Figuring out the deceased’s final moments can help investigators corroborate people’s
stories to ultimately hone in on the killer.
But how do you do that?
There are a few traditional ways to tell when someone died.
Forensic examiners can measure body temperature, skin color, and degree of rigor mortis.
Each of these changes as the body begins decomposing, so knowing the stage of change they can work
backwards to figure out the time of death.
But all those methods only really work in the first 72 hours; any longer and those factors
have piqued, meaning the changes have happened and there’s no more data to glean.
So, when a body has been a corpse for more than three days, investigators have to use
other methods to determine the time of death… one way is to look at all the different insects
that feed on dead human flesh.
*gross sound*
Insects are drawn to the gasses and fluids released from a decomposing body; to them,
it’s fertile ground to lay their eggs and cultivate their young.
*disgust face* The first insect to reach a corpse is usually a blowfly, which will lay
eggs within two days of the person’s death.
Flesh flies also move in early in the decaying process.
Decomposing body fat attracts hide beetles and pyralid moths.
As time go by and flesh breaks down, other species of flies and beetles that have mouths
to chew tougher food move in, consuming that dead flesh.
From there, the corpse becomes an ecosystem with insects feeding on the corpse also feeding
on each other.
This is all super gross but super important.
Entomologists know the life cycles of these insects, specifically the all-important blowfly
that lays its eggs in the dead body first.
When determining time of death, they can look at the stage of development of the blowfly
— whether it’s an egg, larva, pupa, or adult — and take into account environmental
factors like heat and insect patterns to work backwards and figure out approximately when
the blowfly laid its eggs, which can tell them the time of death.
We’re really good at this, but there’s a problem…
we need to know exactly what species that larva is.
And they all sort of look alike.
The examiner needs to know the species for a better estimation of development time and
time of death.
They can do a DNA test on an egg, but that can be pricey.
The cheaper option is to collect the egg and let it grow to adulthood in a lab to figure
out the species, and work backwards from there.
Of course, if you’re trying to find out who killed someone and left them in a field…
waiting three or so days for a fly egg to become a fully-formed insect is stressful.
A criminal can flee to a new country by then!
Knowing the egg-identification thing is an issue, an organic chemist teamed up with a
forensic entomologist to apply real-time mass spectrometry to blowfly eggs.
And it could be a game changer to forensic science.
Before we get to that though, they had to learn about all these species of flies.
To do that, the researchers put pork liver in traps hidden around Manhattan.
This is real science.
They attracted four species of blowfly, and trapped them before they laid their eggs.
They determined their species and then put them on a fresh liver to seed with their spawn.
That way they knew what species were laying eggs where.
Then they collected the eggs and tested each in a mass spectrometer to get a chemical fingerprint.
Mass spectrometry is really complicated to explain, but basically: a sample is ionized,
the atoms are sorted by mass and charge and it gives you a graph that looks like this.
With this we can figure out what atoms something is made of, what they call the chemical fingerprint.
And since everything is made of atoms, we can apply this technology to things like uncovering
the amino acids in blowfly eggs!
Knowing the species then analyzing the eggs gave them the first ever chemically-based
way to identify blowfly eggs, and it only takes minutes to do it!
Ideally, if this tech works, entomologists can use all the data from the crime scene
and a quick mass spectrometry check of the fly larvae to find an approximate time of
death.
But, we can’t use this to catch criminals yet.
Scientists will need to measure the chemical signature of more species, and then create
a database against which spectra of unknown eggs can be compared.This promises to advance
forensic entomology, and by extension help investigators act quickly when faced with
a dead body in a field.
But let’s say no one found the body in the field until it was picked clean by insects…
then forensic examiners have to figure out what happened using just a skull!
I talk about that in this episode right here.
Did you make it through this video without vomiting?
I almost didn’t.
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