Forensic Chemistry and Toxicology

FORENSIC CHEMISTRY AND TOXICOLOGY
The word FORENSIC comes from the Latin term forēnsis, meaning "of or before the forum".
The history of the term originates from Roman times, during which a criminal charge meant
presenting the case before a group of public individuals in the forum.
CHEMISTRY, from the Greek word (khēmeia) meaning "cast together" or "pour together", is the
science of matter at the atomic to molecular scale, dealing primarily with collections of atoms, such as
molecules, crystals, and metals.
FORENSIC CHEMISTRY is the application of chemistry and its subfield, forensic toxicology, in a legal
setting.
A FORENSIC CHEMIST can assist in the identification of unknown materials found at a crime scene.
Specialists in this field have a wide array of methods and instruments to help identify unknown
substances.
 Forensic chemists prefer using nondestructive methods first, to preserve evidence and to
determine which destructive methods will produce the best results.
 Forensic chemists analyze non-biological trace evidence found at crime scenes in order to
identify unknown materials and match samples to known substances.
 They also analyze drugs/controlled substances taken from scenes and people in order to identify
and sometimes quantify these materials.
PHYISICAL EVIDENCE
 Refers to any item that comes from a nonliving origin, while biological evidence always
originates from a living being.
 The most important kinds of physical evidence are fingerprints, tire marks, footprints, fibers,
paint, and building materials .
 Biological evidence includes bloodstains and DNA .
SCOPE OF FORENSIC CHEMISTRY
1. It includes the chemical side of criminal investigation.

2. It includes the analysis of any material the quality of which may give rise to legal proceeding.
3. It is not limited to purely chemical questions involved in legal proceedings.
4. It has invaded other branches of forensic sciences notably legal medicine, ballistics, questioned
documents, dactyloscopy, and photography.
ROLE OF THE FORENSIC CHEMIST IN CRIMINAL INVESTIGATION
1. The forensic chemist's job is to examine evidence given to them from a crime scene, when it
happened and even who committed the crime at times. Forensic chemistry deals with the
chemical analysis of a variety of types of physical evidence.
2. Forensic Chemists apply the scientific method to the investigation of evidence used by law
enforcement agencies and to the analysis of materials and systems in the manufacturing
industry.
3. Forensic Chemists are scientists who apply their forensic chemistry degree to provide evidence
in the prosecution or defense of a crime or lawsuit.
Primary reasons which may contribute to the Destruction of Physical Evidence?
 Improper packing of specimen

 Failure of identification of specimen
 Improper, precaution use in transmitting the specimen.
WHO MAY BE WITNESS?
A Lay witness — the most common type — is a person who watched certain events and describes what
they saw.
An Expert witness is a specialist — someone who is educated in a certain area. They testify with respect
to their specialty area only.
A character witness is someone who knew the victim, the defendant, or other people involved in the
case. Character witnesses usually don’t see the crime take place but they can be very helpful in a case
because they know the personality of the defendant or victim, or what type of person the defendant or
victim was before the crime. Neighbors, friends, family, and clergy are often used as character
witnesses.
DIFFERENCE BETWEEN AN ORDINARY WITNESS WITH AN EXPERT WITNESS?
ORDINARY WITNESS
 someone who personally saw or heard something about the crime.

 a person who was at the scene of the crime
 Do not give opinion
EXPERT WITNESS
 May testify as to her/his opinion

 A witness can be a expert based on his/her knowledge skill training and education and
experience
 Sufficient fact/data/realible/principle/methods
QUALIFICATIONS OF AN ORDINARY WITNESS
 He/she must, with understanding, take the oath or a substitute. Evid.

 He/she must have personal knowledge about the subject of his testimony.
 He/she must remember what he perceived.
 He/she must be able to communicate what he perceived.
 Must possess witness capacity and have personal knowledge of facts relevant to the case.
 Be able to understand the obligation to tell the truth.
 Take the oath or affirm that he or she will testify truthfully.
THE GOLDEN RULES IN THE PRACTICE OF FORENSIC CHEMISTRY
1. Go slowly
2. Be thorough
3. Take notes
4. Consult others
5. Use imagination
6. Avoid complicated theories

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FORENSIC CHEMISTRY AND TOXICOLOGY

SCOPE OF FORENSIC CHEMISTRY

1. It includes the chemical side of criminal investigation.

ROLE OF THE FORENSIC CHEMIST IN CRIMINAL INVESTIGATION

Primary reasons which may contribute to the Destruction of Physical Evidence?

 Improper packing of specimen

WHO MAY BE WITNESS?

DIFFERENCE BETWEEN AN ORDINARY WITNESS WITH AN EXPERT WITNESS?

 someone who personally saw or heard something about the crime.

 May testify as to her/his opinion

QUALIFICATIONS OF AN ORDINARY WITNESS

 He/she must, with understanding, take the oath or a substitute. Evid.

THE GOLDEN RULES IN THE PRACTICE OF FORENSIC CHEMISTRY

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