Introduction to Forensic Chemistry and Toxicology

Study Notes

Forensic chemistry and toxicology involve the chemical aspects of criminal investigations.
Analysis of materials relevant to legal proceedings is critical.
Applications extend beyond purely chemical questions to areas like legal medicine, ballistics, questioned documents, dactyloscopy, and photography.
Examples of forensic chemistry and toxicology applications include:
- Determining if a location is a clandestine laboratory.
- Examining marked bills or suspects in extortion cases.
- Performing paraffin tests.

Collection or reception of specimens/evidence:
- Ensure sufficient sample size.
- Secure a standard for comparison.
- Maintain individuality of the sample.
- Properly label and scale the sample.
Examination of the specimen.
Communication of the examination results.
Court apparatus:
- Present evidence to the court.

Direct Evidence: Directly establishes the main fact of an issue. It is based on the witness's sensory experiences (sight, hearing, smell, touch, taste).
Indirect/Circumstantial Evidence: Establishes a fact by proving another fact. It seeks to establish a conclusion through inferences from proven facts.
Real Evidence: Comprises tangible objects presented in court to prove or disprove a fact. It speaks for itself and requires no further explanation.

Real or Autoptic Evidence: Evidence that addresses the senses of the court. It includes not only sight but also hearing, taste, smell, and touch.
Testimonial Evidence: Expert witness testimony in court. This involves a solemn declaration made orally under oath, responding to lawyer's questions. It is the expert's description of factual truth.
Experimental Evidence: Evidence requiring expert witness demonstration through experiments to prove a point. The court may or may not allow this kind of evidence.
Documentary Evidence: Any written evidence presented by an expert in court, relevant to the case, and not excluded by the Rules of Court.

Ordinary Witness: Can state facts, but not opinions or conclusions. They can testify about general observations (like vehicle speed or voice characteristics).
Expert Witness: Possesses specialized skills or knowledge beyond general understanding. They can provide opinions and conclusions based on their expertise.
Eye Witness: Someone who saw the act in question.
- They must have the capability to perceive and communicate their perceptions to others.
- They must not fall under any exceptions to witness qualifications outlined in the Rules of Court.

An ordinary witness can only state what they perceived, while an expert witness can also provide opinions, deductions, and conclusions based on their perceptions.
An ordinary witness may not be skilled in the area they are testifying about, while an expert witness must be skilled in their art, science, or trade.
An ordinary witness cannot testify about things they have not personally perceived, while an expert witness can testify about things they have observed, providing their opinions and conclusions.