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When Does DNA Evidence Fail?

  Introduction DNA (Deoxyribonucleic Acid) is considered one of the most powerful tools in modern forensic science. It can identify individuals, link suspects to crime scenes, and even exonerate innocent people. Because of its accuracy, DNA evidence is often seen as infallible. However, in reality, DNA can fail under certain conditions. DNA evidence is not always available, usable, or reliable. This blog explains when, how, and why DNA evidence fails, especially in forensic investigations. 1. Effect of High Temperature on DNA High temperature is one of the biggest enemies of DNA. Extreme heat causes DNA degradation Hydrogen bonds between base pairs break The DNA strands fragment into small pieces Examples: Burnt bodies Fire accident crime scenes Explosions or bomb blasts 👉 In such cases, DNA may be too damaged to analyze, making identification difficult or impossible. 2. Effect of Time (Old or Degraded Samples) DNA does not last forever. Over time, DNA naturally breaks down Enzyme...
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Forensic Case Study Report: The Zodiac Killer

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 1. Introduction The Zodiac Killer is one of the most infamous unidentified serial killers in history. He operated in Northern California, USA, between 1968–1974 and taunted law enforcement by sending cryptic letters, ciphers, and symbols to newspapers and police. Despite decades of investigation, the killer’s true identity remains unknown. •Confirmed Victims: 5 •Claimed Victims (letters): Up to 37 •Primary Modus Operandi: Attacks on couples in secluded areas, followed by communication with media and police 2. Crime Details (Timeline of Major Attacks) 2.1 Lake Herman Road – 20 Dec 1968 •Victims: Betty Lou Jensen (16), David Faraday (17) •Attack: Shot multiple times while sitting in their car. •Forensic Evidence: Shell casings recovered, but no fingerprints or DNA at the time. 2.2 Blue Rock Springs – 4 July 1969 •Victims: Darlene Ferrin (22), Michael Mageau (19) •Attack: Gunfire into parked vehicle. Darlene killed instantly, Mageau survived with injuries. •Surviving witness gave vag...
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