Unit 5: The Typologies of Crime and Law

Forensic science operates inside a legal framework that decides what counts as a crime, who the parties are, and what evidence a court will accept. The vocabulary below is the shared language of investigators, lawyers and courts; precise use of each term is what allows a scientific finding to become legally admissible proof.

• Substantive vs procedural law: Substantive law defines the act (what is prohibited); procedural law governs how it is investigated, tried and proved.
• Burden of proof: In criminal matters the prosecution must prove guilt "beyond reasonable doubt," a higher standard than the "balance of probabilities" used in civil cases.
• Two-part crime rule: Most crimes require both a guilty act (actus reus) and a guilty mind (mens rea), joined at the same moment.
• Forensic link: Physical evidence bridges the crime scene, the victim and the culprit; its legal value depends on an unbroken chain of custody.

II. Crime and the Categories of Offence — what the law prohibits

The law distinguishes conduct that harms society and defines how seriously the state treats it.

A. Defining crime

A crime is an act or omission that violates a public law and is punishable by the state.

• Public wrong: Prosecuted by the state, not the injured party — e.g. theft is State v. Accused, not victim v. accused.
• Elements: Requires a prohibited act plus, usually, a culpable mental state.
• Sanction: Punishable by fine, imprisonment or death, unlike a civil wrong (tort) which attracts compensation.

B. Offence

An offence is any act or omission made punishable by law; in practice it is used interchangeably with crime.

• Statutory basis: Every offence is created by a statute defining the act and its penalty.
• Classification: Graded by seriousness (petty, minor, serious) and by procedure (see below).

C. Cognizable offence

A cognizable offence is one in which police may arrest without a warrant and begin investigation without a magistrate's order.

• Nature: Generally serious — murder, rape, robbery, kidnapping.
• Police power: An FIR (First Information Report) is registered and investigation starts immediately.
• Rationale: The gravity and urgency justify immediate state action.

D. Non-cognizable offence

A non-cognizable offence is one in which police cannot arrest without a warrant and need magisterial permission to investigate.

• Nature: Comparatively minor — simple assault, defamation, public nuisance.
• Procedure: The complaint is entered, but the informant is directed to the magistrate; investigation follows only on the court's order.
• Contrast with (C): Severity governs which category applies, and thus the extent of police discretion.

III. The Crime Scene — the source of physical evidence

The crime scene is where forensic and legal worlds first meet.

A. Crime scene

A crime scene is any location where a crime occurred or that yields physical evidence connected to it.

• Types: Primary (where the act occurred), secondary (where related evidence is later found, e.g. a dump site).
• Locard's exchange principle: "Every contact leaves a trace" — perpetrator and scene exchange material (fibres, blood, prints).
• Protection: Cordoned and secured to prevent contamination, which would compromise later admissibility.
• Documentation: Photographed, sketched and noted before any item is moved.

IV. Parties to Criminal Proceedings — the people the law names

Each participant in a case has a defined legal role and status.

A. Victim

The victim is the person harmed, injured or killed by the criminal act.

• Role: Often the complainant and a key witness; may receive state compensation.
• Forensic relevance: The victim's body or property frequently carries trace evidence linking to the culprit.

B. Culprit

The culprit is the person who actually committed the offence — the guilty party in fact.

• Distinction: A factual label for the true offender, used before or independent of a formal charge.
• Contrast with accused: One may be accused yet not the real culprit.

C. Accused

The accused is a person formally alleged, in a criminal proceeding, to have committed the offence.

• Legal status: Presumed innocent until proven guilty.
• Rights: Silence, legal representation, and a fair trial.

D. Defendant

The defendant is the party against whom a case is brought and who defends it in court.

• Usage: "Accused" is common at the investigation/charge stage; "defendant" during the trial. In civil suits the defendant answers a claim rather than a charge.

E. Prosecution

The prosecution is the party, representing the state, that brings and argues the case against the accused.

• Duty: To prove guilt beyond reasonable doubt and to disclose evidence fairly.
• Actors: Public prosecutor or district attorney, supported by investigating police.

F. Conviction

A conviction is a court's formal finding that the accused is guilty of the charged offence.

• Effect: Followed by sentencing (fine, imprisonment, etc.).
• Opposite: Acquittal — a finding of not guilty.
• Threshold: Requires proof beyond reasonable doubt.

V. Witnesses and Testimony — how facts reach the court

Witnesses supply the evidence on which findings rest; their type governs how much weight the court gives.

A. Witness

A witness is a person who gives evidence, on oath, about facts relevant to a case.

• Duty: To testify truthfully; false testimony is perjury.
• Basis: Personal knowledge, observation or expertise.

B. Expert

An expert is a person with specialised knowledge, skill or training in a field beyond ordinary experience.

• Fields: Forensic medicine, ballistics, toxicology, handwriting, DNA.
• Role: Supplies informed opinion where laypersons cannot judge.

C. Expert witness

An expert witness is an expert who gives opinion evidence in court on matters within their expertise.

• Special power: Uniquely permitted to state opinions, not just observed facts.
• Example: A forensic pathologist testifying that wounds indicate homicide, not suicide.
• Weight: Persuasive but not binding — the court is the final judge.

D. Eye witness

An eye witness is a person who personally saw the event or its relevant parts.

• Value: Direct evidence of high probative weight.
• Limitation: Vulnerable to memory error, poor lighting, and suggestion.

E. Hear-say witness

A hear-say witness testifies to what another person told them, not to what they directly perceived.

• General rule: Hearsay is inadmissible because the original speaker cannot be cross-examined.
• Contrast with (D): The eye witness reports first-hand perception; the hearsay witness relays second-hand information, generally excluded save for defined exceptions (e.g. dying declarations).

VI. The Elements and Signatures of Crime — proving and characterising the act

These concepts establish that a crime happened, that the accused is culpable, and how the offender operates.

A. Actus reus

Actus reus is the physical, external element of a crime — the guilty act.

Crime = actus reus + mens rea (concurring in time)

• Forms: A positive act (striking a blow), an omission where a duty exists (a guardian failing to feed a child), or a state of affairs.
• Requirement: Must be voluntary; a reflex or convulsion is not an actus reus.

B. Mens rea

Mens rea is the mental element — the guilty mind or blameworthy intention.

• Levels: Intention, knowledge, recklessness, negligence, in descending culpability.
• Concurrence: Must coincide with the actus reus for liability.
• Exception: Strict-liability offences (e.g. some regulatory acts) need no mens rea.

C. Corpus delicti

Corpus delicti ("body of the crime") is the proof that a crime has actually been committed.

• Meaning: Not literally a corpse — it is the set of facts showing a crime occurred, e.g. a burned building for arson.
• Rule: A conviction cannot rest on a confession alone; the corpus delicti must be independently established.

D. Modus operandi

Modus operandi (MO) is the characteristic method or pattern by which an offender commits crimes.

• Use: Links a series of offences to one perpetrator through repeated technique (same entry method, same weapon).
• Distinction from signature: MO is functional (how the crime is done); a signature is the offender's personal, unnecessary ritual.

VII. Chain of Custody — keeping evidence admissible

A. Chain of custody

The chain of custody is the documented, unbroken record of the seizure, handling, transfer, and storage of physical evidence.

• Purpose: To prove the evidence in court is the same item collected, unaltered and uncontaminated.
• Record contents: Who collected it, when and where, every transfer, and secure storage details.
• Consequence of breakage: A gap allows the defence to challenge integrity, and the evidence may be ruled inadmissible.
• Forensic anchor: A blood sample must be sealed, labelled, signed at each handover, and stored under controlled conditions from scene to laboratory to courtroom.