"Unlocking Crime Mysteries: The Seven Principles of Forensics"

During criminal investigations, forensic professionals can preserve scientific objectivity, accuracy, and integrity by adhering to the seven principles of forensic science. These guidelines guarantee that evidence is gathered, examined, and interpreted in a way that is trustworthy and acceptable in court.

Blog Jul 2, 2025 0 47 Add to Reading List

"Unlocking Crime Mysteries: The Seven Principles of Forensics"

Here are the Seven Principles of Forensic Science:

Principle	Key Idea	Example
Law of Individuality	Everything is unique	Fingerprint match
Law of Progressive Change	All things change over time	Body decomposition
Law of Comparison	Only like should be compared	Blood to blood
Law of Analysis	The whole understood by its parts	Paint chip analysis
Law of Circumstantial Facts	Facts are objective, unlike people	Weapon with fingerprints
Law of Probability	Forensic results are probabilistic	DNA match probability
Law of Exchange	Contact leaves trace	Hair left at crime scene

1. Law of Individuality

Every object, natural or man-made, has a unique identity

Not even identical twins or manufactured objects are exactly alike in the world. This distinctiveness is what forensic specialists use to link fingerprints, bullets, writings, DNA, and other items to a particular source. For instance, a fingerprint discovered at a crime scene can be identified as belonging to a single person.

2. Law of Progressive Change

Everything changes over time

Physical and biological evidence can change or deteriorate. The integrity of evidence can be impacted by time, environment and handling (e.g., fading of prints, decomposition of a body).

3. Principle of Comparison

Only like can be compared with like

The only way to compare evidence is using a recognised reference or standard. For instance, it is necessary to compare the suspect's shoe print with one that was discovered at the scene.

4. Principle of Analysis

The analysis can be no better than the sample analyzed

Only standardised, accurate, and trustworthy methods should be employed. guarantees the forensic results' objectivity and reliability.

5. Law of Circumstantial Facts

Facts do not lie, but witnesses can

Eyewitness reports are not as trustworthy as physical proof. When read correctly, circumstantial evidence frequently reveals the truth more precisely.

6. Principle of Probability

Forensic conclusions are based on probability, not certainty

In forensic science, absolute assurance is uncommon. To ensure scientific accuracy, results are presented as likelihood or probability.

7. Principle of Exchange (Locard’s Exchange Principle)

Whenever two objects come into contact, there is always an exchange of materials

Praposed by Dr Edmond Locard. Hair, fibres, skin cells, and other items are always brought into the crime scene by criminals and taken away by them. This serves as the foundation for trace evidence.