Unit-2 Types of Evidence:

 Unit-2 Types of Evidence:

 

Forensic evidence is one of the most powerful tools in modern investigations. It provides scientific, unbiased, and reliable proof that helps uncover the truth and ensure justice.

 

The following are the types of evidence in forensic science

·         Physical evidence: Weapons, tools, and other tangible objects.

·         Biological evidence: Blood, hair, bodily fluids, and tissues.

·         Chemical evidence: Drugs, explosives, and trace substances.

·         Digital evidence: Data from electronic devices and online sources.

 

 Physical evidence-

Weapons – weapons are one of the most significant forms of physical evidence in forensic science. They are tangible objects used to commit a crime or cause harm, and they can provide direct links between the suspect, the victim, and the crime scene.

For example:

1.   Firearms – pistols, rifles, shotguns, along with ammunition, shell casings, and magazines.

2.  Sharp-edged weapons – knives, daggers, swords, or broken glass pieces used to stab or cut.

3. Blunt weapons – hammers, clubs, metal rods, or any heavy object used to strike.

4.      Improvised weapons – everyday objects adapted to cause injury, such as tools or household items.

Tools and other tangible objects- These are a key category of physical evidence in forensic science. They are real, solid items that can be touched, measured, and examined, and they often play a direct role in committing or concealing a crime.

For example:

1.      Tools – Examples include screwdrivers, crowbars, pliers, hammers, saws, or drills. These may be used for breaking into buildings, tampering with locks, or even causing injury.

2.      Other Tangible Objects – Items such as ropes, chains, clothing, broken glass, locks, or personal belongings found at the scene. These can be directly linked to the suspect, victim, or crime location.

Biological evidence- It refers to any sample from a living organism, human, animal, or plant that can be used in forensic investigations. In criminal cases, human biological evidence is especially important because it often contains DNA or other unique biological markers that can link a suspect, victim, and crime scene.

Some of the biological evidence is

1.      Blood

2.      Hair

3.      Bodily fluid

4.      Tissue 

Blood- A vital body fluid made of red blood cells, white blood cells, platelets, and plasma.

 DNA profiling from white blood cells can identify individuals with high accuracy.

Bloodstain pattern analysis reveals how and from where blood was deposited, helping reconstruct events.

 Hair- Composed mainly of keratin, with a root that may contain nuclear DNA and a shaft that can provide mitochondrial DNA.

Importance in forensic:

·         Microscopic examination can determine species, body area, and sometimes racial characteristics.

·         DNA from the root can match a person exactly; mitochondrial DNA from the shaft can link to maternal lineage.

 

Bodily Fluids- Includes saliva, semen, urine, sweat, and vaginal secretions.

Importance in forensic:

·         Saliva: DNA from cheek cells; often found on cigarette butts, envelopes, or bite marks.

·         Semen: Contains sperm cells and enzymes; crucial in sexual assault cases.

·         Urine and sweat: May reveal drug use or toxins.

Tissues- Samples of skin, muscle, or internal organs.

Importance in forensic:

·         Provide DNA for identification when other evidence is degraded.

·         Can reveal injuries, diseases, or exposure to toxins.

·         Useful in mass disasters or cases with decomposed remains.

 Chemical evidence refers to any substance whose composition can be scientifically analyzed to provide information about a crime.

It includes .

1.      Drugs,

2.      Explosives,

3.      Trace chemical

Drugs- It Can be illegal narcotics (heroin, cocaine, methamphetamine), prescription medications, or controlled substances.

Importance in forensic:

·         Helps determine whether possession, trafficking, or manufacturing occurred.

·         Can reveal patterns of abuse or poisoning.

Explosives- It Includes commercial explosives (TNT, dynamite), military-grade materials (RDX, PETN), and homemade devices (pipe bombs, improvised mixtures).

Importance in forensic:

·         Identifies the explosive type and chemical composition.

·         Matches residues from a blast site to materials found with a suspect.

·         Helps reconstruct how and when the device was made and detonated.

Trace Substances- Very small amounts of chemical material, such as paint chips, glass fragments, lubricants, soil, or gunshot residue.

Importance in forensic:

·         Even microscopic traces can link a suspect to a scene or object.

·         Paint or fiber analysis can connect vehicles, tools, or clothing to a crime.

·         Gunshot residue can confirm if a person recently fired a weapon.

 Digital evidence-It is any information stored or transmitted in digital form that can be used in an investigation or legal case. It comes from electronic devices, online platforms, and digital storage systems, and is often crucial in solving modern crimes.

Sources of Digital Evidence

• Computers and Laptops – Store documents, emails, browsing history, images, and even deleted files that can be recovered.
• Mobile Devices – Contain text messages, call logs, GPS location data, app usage records, and photos/videos.
• Cloud Services – Platforms like Google Drive, Dropbox, and iCloud store documents, backups, and shared files.
• Social Media Platforms – Posts, messages, images, and videos from sites like Facebook, Instagram, and X (Twitter) can reveal activities, connections, and timelines.
• Websites and Online Accounts – Browsing history, online purchases, and account activity logs.
• Network Logs – Records from servers, routers, and firewalls showing connections, IP addresses, and data transfers.