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Navigating The Fine Line Between Proof and Possibility

While DNA testing has earned its place as a cornerstone of forensic science, the question persists: How precise and conclusive is it when it comes to establishing guilt or innocence? Lately, concerns about potential wrongful convictions or acquittals have come to the forefront, casting doubt on the reliability of DNA evidence.

Understanding DNA

Deoxyribonucleic acid (DNA) serves as one of the fundamental building blocks of human life, it is responsible for shaping an individual's distinct characteristics.

Virtually every cell within the human body contains DNA, and it can be found in a multitude of bodily components – such as blood, skin cells, tissue, teeth, hair, saliva, mucus, perspiration, fingernails, and more. Notably, cells found in saliva are notably rich sources of DNA.

The DNA Evidence Trail: Possible Sources at a Crime Scene

In a criminal investigation, identifying the potential locations of DNA evidence is essential. DNA can be found in various forms depending on where it's sourced.

Here's a breakdown of possible locations and their corresponding DNA sources:

  • Bite mark or area licked: Saliva

  • Fingernail scrapings: Blood or skin cells

  • Blankets, sheets, pillows, or other bed linens: Semen, sweat, hair, or saliva

  • Clothing: Hair, semen, blood, or sweat

  • Hat, bandanna, or mask: Sweat, skin cells, hair, or saliva

  • Tissue, washcloth, or similar item: Saliva, semen, hair, skin cells, or blood

  • Cigarette butt; toothpick; or rim of bottle, can, or glass: Saliva

  • Tape or ligature: Skin cells, saliva, or hair

As there are various sources in which DNA can be found, the act of interpreting the findings can be extremely complex, making meticulous DNA analysis crucial.

The DNA Examination Process

At a crime scene, specialized Crime Scene Officers skilled in DNA evidence collection are tasked with gathering potential DNA evidence. This can involve samples from bodily fluids like blood and saliva or employing techniques like 'tape lifts' to recover DNA from surfaces and items.

The legal framework, established under the Crimes (Forensic Procedures) Act 2000, empowers both the police and the courts to conduct forensic procedures on individuals, allowing for the collection of blood, buccal (spit) samples, hair, or fingerprints.

The actual analysis of DNA samples and profiles falls under the purview of scientists employed by the Forensic & Analytical Science Service (FASS). These experts possess specialised knowledge in DNA analysis and can identify different DNA profiles derived from a source, along with the quantity of DNA recovered.

However, FASS scientists cannot determine the origin of the DNA or how it came to be at the scene.

Misuse of DNA Evidence

The misuse of DNA evidence in the criminal justice system is a significant concern. Errors in the collection of DNA samples, contamination at crime scenes or in laboratories, misinterpretation of complex DNA profiles, and confirmation bias can all lead to unreliable evidence. Prosecutorial misconduct, where unreliable or unverified DNA evidence is presented in court, can result in wrongful convictions. The retesting of evidence in some cases has led to post-conviction exonerations, revealing the potential for misuse.

The Complexities of Transference

A pivotal concept in the examination of DNA is that of 'transference,' particularly 'secondary transfer.'

In our daily lives, we continually shed DNA, unknowingly leaving traces behind.

Subsequently, this genetic material can be picked up by other individuals or objects, creating the potential for it to be transferred to unexpected places.

DNA as Circumstantial Evidence

From a legal standpoint, DNA is often categorised as "circumstantial evidence." Unlike direct evidence, which directly proves a fact, circumstantial evidence merely suggests a possibility.

The strength and relevance of DNA evidence can vary widely from case to case.

For example, if a murder occurred in a shared living space, the presence of a roommate or partner's DNA may hold little or no value.

Conversely, if a complete stranger's DNA is found on a deceased person located in a car trunk, that DNA evidence may carry greater weight.

It is crucial for judges and juries to exercise caution, and not fall victim to the misconception that DNA is an infallible method of establishing guilt in a case.

Do You Need Legal Guidance?

Navigating the intricacies of DNA evidence in legal matters can be challenging.

If you require legal assistance or have questions about DNA evidence in criminal cases, don't hesitate to contact Creevey Horrell Criminal Lawyers today.

Contact Creevey Horrell Criminal Lawyers

Based in Brisbane, Roma, Toowoomba, and Townsville.

Visit to contact us today.


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