\n<\/p>\n
A mass of writhing maggots on a decomposing murder victim is not a sight for the squeamish, but for some, it is evidence. A maggot\u2019s age and species can give essential information to forensic entomologists investigating murders. (A single wriggling horse fly maggot, for instance, found on a dead body far from water, gave entomologists in 2022 a key lead to where the body came from.) Combing through these fly larvae, investigators can potentially learn when and where a crime happened, whether the body has been moved or whether toxins were involved.<\/p>\n
For example, blowflies are among the earliest insect colonizers of corpses; they typically sniff out and lay eggs on a dead body within minutes to hours. How fast the maggots (also called larvae) develop depends on heat, humidity, and the insect\u2019s species and sex. To use this evidence, investigators typically must grow the larvae until adulthood in a laboratory setting and then identify them, either visually or by genetic sequence. But what if the larvae are dead or missing, there\u2019s no high-quality DNA or there isn\u2019t the time\u2014or equipment\u2014to sequence the flies\u2019 genomes? \u201cPeople in a crime lab simply do not have the resident expertise or the resources to be able to routinely conduct DNA analysis on insect evidence,\u201d says Rabi Musah, a bioorganic chemist at Louisiana State University.<\/p>\n
To tackle these challenges, Musah and other researchers have combined machine-learning algorithms with methods such as infrared spectroscopy and chemical profiling to quickly pinpoint maggots\u2019 species and sex. Such tools could help experts rapidly identify the maggots without the larvae\u2019s DNA or without the larvae altogether, only what they leave behind\u2014saving time and money usually spent in sequencing. They could also help investigators take measurements at the scene of the crime itself to determine larval sex.<\/p>\n
If you’re enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.<\/p>\n
Musah measured the chemical profiles, called the metabolome, of insect eggs, larvae and pupae using a type of mass spectrometry\u2014a technique that can tease apart molecules called metabolites based on their mass and charge. With these data, she and her team are building a large metabolome database for most of the insects that colonize decomposing remains. Her team\u2019s machine-learning algorithm trained on the data would let investigators using a mass spectrometer, which is less expensive and much easier to use than a DNA sequencer, reliably match a new chemical profile to an insect species in less than five minutes.<\/p>\n
A similar approach can work even without the larvae themselves. Sometimes people come across fully decomposed bodies many months or years after a murder. By that time the larvae are long gone, Musah says, and the only remaining insect evidence is the hard shell-like exteriors of the pupae, tools of metamorphosis discarded after the larvae become adult flies.<\/p>\n
It\u2019s impossible to identify pupae coverings with the naked eye, and in many cases, the DNA contained within them is too old and degraded for sequencing. But as Musah\u2019s group reported in a recent paper in Forensic Chemistry, their method\u2014of chemical fingerprinting followed by machine-assisted classification\u2014works with casings, too. Finding the chemical profile of casings can even reveal toxins in the victims\u2019 bodies because the larvae tend to store them in their pupal coverings. (The rate of molecular breakdown might also someday point to the casings\u2019 ages.)<\/p>\n
Other groups are also trying to use machine learning to catalog crime scenes\u2019 larval visitors: for instance, a team of Texas A&M researchers recently developed a method that combines infrared measurements from a handheld device with machine learning to identify blowfly larvae\u2019s sexes.<\/p>\n
Male and female larvae develop at different speeds and can help investigators pinpoint when they first colonized remains, but their sexes are indistinguishable by eye. To identify sexes, investigators can crush the larvae and amplify their DNA using PCR, which is time-consuming, renders the larvae useless for any further studies, and has only an 80 percent chance of working correctly. Aidan Holman, a Texas A&M toxicology graduate student, and his colleagues set out to find larvae\u2019s sexes without having to mash them up.<\/p>\n
After first rearing the male and female larvae separately, Holman\u2019s group used a handheld infrared spectroscopy device to \u201czap\u201d them and measure the light released. The proteins, fats and other molecules that make up the larvae scatter the light in unique ways, generating a specific \u201cspectral signature\u201d based on sex. The researchers then trained a machine-learning model on this spectral data and found that it could predict the larvae\u2019s sex with more than 90 percent accuracy. Next, they will collect data from a much bigger selection of flies to train their model.<\/p>\n
Murdoch University forensic entomologist Paola Magni, who is not involved in either project, emphasizes that these machine-learning databases will need to be officially vetted, as DNA sequence banks are, so results aren\u2019t later overturned legally. And use of AI more broadly in this process can be risky, she adds. \u201cThe flip of the coin of artificial intelligence can become very dangerous in a forensic context because you can really cause a miscarriage of justice,\u201d she says. Plus, she and Musah both highlight that more research is needed into how other substances in the body might skew molecular markers\u2014and Musah is pulling data from across as large and global an insect sample as possible to find the markers that remain constant. \u201cThe enhancement and expansion of the database involves a never-ending process,\u201d Musah says.<\/p>\n
Texas A&M forensic entomologist Jeff Tomberlin, who was also not involved in either project, believes that cutting-edge methods like machine learning should be integrated into forensic case work. But, he notes, their long-term accuracy, precision and potential biases need to be carefully studied as well. \u201cWe\u2019re in the infancy of applying these methods in this particular realm,\u201d he says. \u201cSo if you think of it like an arc, we\u2019re at the beginning of the arc.\u201d<\/p>\n
If you enjoyed this article, I\u2019d like to ask for your support. Scientific American<\/span> has served as an advocate for science and industry for 180 years, and right now may be the most critical moment in that two-century history.<\/p>\n I\u2019ve been a Scientific American<\/span> subscriber since I was 12 years old, and it helped shape the way I look at the world. SciAm <\/span>always educates and delights me, and inspires a sense of awe for our vast, beautiful universe. I hope it does that for you, too.<\/p>\n If you subscribe to Scientific American<\/span>, you help ensure that our coverage is centered on meaningful research and discovery; that we have the resources to report on the decisions that threaten labs across the U.S.; and that we support both budding and working scientists at a time when the value of science itself too often goes unrecognized.<\/p>\n In return, you get essential news, captivating podcasts, brilliant infographics, can’t-miss newsletters, must-watch videos, challenging games, and the science world’s best writing and reporting. You can even gift someone a subscription.<\/p>\n There has never been a more important time for us to stand up and show why science matters. I hope you\u2019ll support us in that mission.<\/p>\n","protected":false},"excerpt":{"rendered":" A mass of writhing maggots on a decomposing murder victim is not a sight for the squeamish, but for some, it is evidence. A maggot\u2019s age and species can give essential information to forensic entomologists investigating murders. (A single wriggling horse fly maggot, for instance, found on a dead body far from water, gave entomologists<\/p>\n","protected":false},"author":1,"featured_media":46340,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[58],"tags":[3892,2173,506,12095,2797,2664,2244,23687],"class_list":{"0":"post-46339","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-analysis","9":"tag-crime","10":"tag-crucial","11":"tag-forensic","12":"tag-larvae","13":"tag-scene","14":"tag-speed","15":"tag-techniques"},"_links":{"self":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/46339","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=46339"}],"version-history":[{"count":0,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/46339\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/media\/46340"}],"wp:attachment":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=46339"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=46339"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=46339"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}