Maggots and barnacles at the murder scene: forensic entomologists’ best friends

Dr Paola A. Magni has spent her life studying how maggots eat human corpses.

If that sentence is too gruesome for you, I’d urge you to close the page – the world of forensic entomology only gets worse from here.  

“Anything that is alive when somebody is dead is my specialty,” Magni told Cosmos Science.

“My PhD research was about the effect of maggot masses of different size – from 100 maggots to 5000 maggots – within three or four days on a body, in a refrigerator.”

We spoke to Magni for a special forensic series on the podcast The Science Briefing. 

The first episode is about time of death, while the other three episodes in the series are covering blood splatter, DNA evidence and issues with forensics. You can listen to episode one below.

For those interested, Magni says maggots work fast, and a body covered in 5000 maggots put in a fridge on Wednesday can be half a body by Saturday.

Maggots are important for forensic entomologists and investigators, as it can help them uncover an approximate time of death.

“Most of the time, pathologists wash away the maggots, and so they remove information,” Magni told Cosmos Science.

“I tag along when there are maggots, because I’m a forensic entomologist … nobody wants to pick up the maggots, and I don’t have a problem with it.”

Using the size of the maggots, and other variables, particularly temperature, forensic researchers work backwards to determine when the maggots arrived. This can give an approximate time of death of the body, which is helpful for determining when a crime may have taken place.

But of course – nothing is ever quite that simple. If the victim has been buried it can take some time for the flies to make it to the body, and if it’s cold, it might take much longer for flies to hatch and start to snack.

“If the body is completely naked in summer in a bush with no problems, well, the flies can land on the body within 15 minutes and start decomposing,” Magni says.

And then there’s suitcases.

“Recently I’ve worked on research using 72 suitcases. The bodies were put in suitcases to see the difference between the colonisation outside, and on a body in a suitcase that is zipped,” she says.

So how do the flies get in? “Don’t worry, they can get in.”

Maggots are all well and good, but Magni also loves aquatic forensics. Particularly important for time of death, she says, is barnacles. Well, barnacle larvae.

“Babies of barnacles live in the top layer of the water. When a body is dumped in the water, the body can be a very good surface to attach to – like a boat.

“The barnacles grow – like insects – based on the environmental temperature, in this case, the water temperature. The barnacles grow in layers.”

“And the layers can be studied in terms of chemicals. The layers and the chemicals are related to the water they travelled, and the species are related to the different parts of the world. So, they can give us information on the travel that they did.”

Who knew that barnacles and maggots are such good timekeepers? For all your other decomposition related questions – like, what other types of mortises are there? You’ll have to listen to our podcast.