Forensic Genomics and Entomology: Unraveling a Crime Scene with Insects, Soil and DNA

Overview

This Royal Institution event takes viewers through a crime scene scenario where entomology, soil science and forensic genetics are used to uncover time since death, locate evidence and interpret DNA profiles. Experts demonstrate field sampling, laboratory analysis, and cutting edge single cell approaches to address complex mixtures of DNA.

Key insights

• Insects can estimate time since death and reveal scene details via larval development and posterior spiracles.
• Soil analysis, including texture, chemistry and crime-scene reconstruction, helps pinpoint locations and transfer pathways.
• DNA evidence ranges from blood and saliva to touch DNA, each with distinct success rates and interpretation challenges.
• The SCANDI project shows a shift toward single cell analysis to resolve DNA mixtures and improve justice outcomes.

Overview

The Royal Institution presents a multi-scene crime-solving scenario that threads together forensic entomology, forensic soil science and forensic genetics to illustrate how modern genomics can aid the justice system. The discussion emphasizes real-world sampling, evidence handling and analytical interpretation while showcasing advanced technologies that push beyond traditional DNA profiling.

Entomology as a Clock at the Scene

Forensic entomology is described as a powerful tool for estimating the post-mortem interval. Doctor Kat Brown explains how a cadaver in a woodland environment hosts a succession of insects, with larvae found in moist areas and unusual placements such as the neck suggesting trauma. The process includes collecting representative samples from multiple locations, rear larvae to adults, preserve others for microscopic analysis, and measure larval features such as posterior spiracles and cephalopharyngeal skeleton. These morphological markers, together with temperature data from the scene, allow an age estimate for the larvae and thus a minimum time since death. The common species Calipiera vicina is used as an example to map larval age to ambient temperature, yielding an approximate six-day age range for the larvae in the scene. The method also acknowledges limitations and stresses that insect age must be contextualized with environmental conditions and insect arrival times at the cadaver.

Soil Evidence as a Geochemical Fingerprint

Soil analysis is introduced as a complementary forensic tool. Soil from the victim’s feet is compared with soils at the locus, using visual observations, CT scans and particle-size distribution analyses guided by Stokes law. The soil appears to be silty loam rather than sandy London clays, enabling investigators to exclude rivers and identify a more precise origin. The soil’s chemical signature is then interrogated by measuring elements such as aluminium, cobalt and zinc to build a layered geochemical fingerprint. By overlaying soil chemistry with known green spaces and land-use patterns, investigators narrow down possible origin points. An artifact analysis using spectrometry reveals road-work fibers matching a nearby roadworks site, aligned with the time window established by soil and entomology data. Finally, vegetation remnants in the victim’s hair, like plane tree seeds, add a corroborating botanical signature and point toward a northern edge of Berkeley Square as a secondary focus for action.

DNA Evidence and Forensic Genetics

Forensic genetics comes to the fore as the table of evidence grows with items such as blood-stained caps, ropes and possibly other biological materials. The discussion turns to how DNA is collected in a contamination-controlled manner and the packaging that maintains chain-of-custody. The talk then shifts to the biology of DNA and the realities of obtaining usable DNA profiles from different sources. Blood provides high-quality profiles in roughly 80-90% of cases, saliva around 63%, and touch DNA on objects can be as low as about 12%. The presenter explains that mixtures—where DNA from multiple individuals is present—are a major interpretation challenge, sometimes resulting in mixtures of the victim, suspect and bystanders. A proposed solution is the SCANDI project, Single Cell Analysis for DNA Intelligence, which aims to separate individual cells from mixtures using fluorescence-activated cell sorting. The idea is that if cells from different people can be isolated, their DNA can be read as individual profiles, potentially enabling database linkage without confounding mixtures. The talk emphasizes the need to educate the justice system about these limitations and to pursue technical advances that translate into better outcomes for victims and fairer convictions.

Case Continuation and Conclusions

Colleagues from soil science, genetics and crime-scene investigation discuss how the integrated approach can tighten timelines, reduce uncertainties and narrow down possible suspects or locations. The session ends with remarks on the importance of taxpayer-funded, credible science and a call for continued collaboration to translate academic innovation into forensic practice that protects the innocent and supports the prosecution of the guilty. The event underscores that modern forensic science is an interdisciplinary effort that combines entomology, soil science, DNA profiling and innovative single-cell technologies to strengthen evidence value in the justice system.