5 Forensic Facts That Sound Made Up — But Aren’t

Forensic scienceDiscover the fascinating field of Forensic Science, the application of scientific principles to legal matters. This post delves into its many disciplines, from DNA analysis to crime scene investigation, its importance in the justice system, Read Full Definition is full of facts that sound like movie fiction — except some of them are completely real. Here are five short forensic facts that are scientifically grounded and genuinely useful.

1. Identical twins can share the same routine DNA profile — but not the same fingerprints

Monozygotic twins originate from the same fertilized egg, so their standard forensic nuclear DNADNA, or Deoxyribonucleic Acid, is the genetic material found in cells, composed of a double helix structure. It serves as the genetic blueprint for all living organisms. Read Full Definition profiles are typically indistinguishable. You can read more about the markers used in routine profiling in our guide to STR analysis. FingerprintsFingerprint, impression made by the papillary ridges on the ends of the fingers and thumbs. Fingerprints afford an infallible means of personal identification, because the ridge arrangement on every finger of every human being is Read Full Definition are different. Ridge patterns are influenced by development in the womb, which is why even identical twins have different fingerprints. For background on ridge-detail examination, see our forensic fingerprint analysis guide.

Why it matters: DNA may not separate identical twins in a routine STR case, while fingerprint evidenceEvidence is any form of proof, such as objects, materials, or scientific findings, presented to establish or disprove a fact in a legal proceeding. It is used to reconstruct events and link or exclude individuals Read Full Definition potentially can.

2. Red blood cells do not contain nuclear DNA

Blood is one of the most important sources of forensic DNA, but the red blood cells themselves are not the source. Mature human red blood cells lack nuclei. Most nuclear DNA recovered from blood comes from white blood cells.

So yes: blood contains DNA, but not because of the cells that give blood its red color.

3. Luminol can reveal hidden blood — but it does not prove that blood is present

Luminol can produce a blue chemiluminescent glow when it reacts with substances associated with blood, making faint or cleaned bloodstain patterns easier to visualize. But it is a presumptive test. Other oxidizing substances and materials with peroxidase activity can also trigger a reaction.

Forensic lesson: a glow is a clue, not a final identification.

4. Teeth can survive when much of the body cannot

Teeth are among the most durable structures in the human body. In decomposed, burned, skeletonized, or mass-fatality remains, dental features and restorations can sometimes be compared with antemortem dental records to help establish identity. Our forensic odontology overview explains how dental evidence is used in identification.

That is why forensic odontology can become crucial when fingerprints or soft-tissue features are no longer available.

5. Insects can help estimate how long a person has been dead

Forensic entomologists study insects associated with decomposing remains. The species present, their developmental stage, and environmental conditions can contribute to estimation of the postmortem intervalThe post-mortem interval (PMI) is the time that has elapsed since an individual's death. When the time of death is not known, the interval may be estimated, and so an estimated time of death is established. Read Full Definition. For a deeper example, see our article on carrion insects in forensic entomology.

But insects are not a perfect biological stopwatch. Temperature, geography, access to the body, and insect species all affect the interpretation.

Forensic fact takeaway

The interesting part of forensic science is not that it produces magical answers. It is that small biological, chemical, and physical details can become evidence when they are collected, tested, and interpreted correctly.

Which forensic fact surprised you most?

Sources

• NIST — Forensic Genetics
• NIST — Forensic Biometrics
• NIJ — Blood Screening Tests
• NIJ — Forensic Anthropology and Odontology
• NIJ — Postmortem Interval Estimation