Forensic Chemistry Introduction

FORENSIC CHEMISTRY : FORENSIC CHEMISTRY By MELCON S. LAPINA, MS CRIM 4th Place, Criminologists Licensure Board Examinations, Manila, October 1996


DEFINITION OF FORENSIC CHEMISTRY : DEFINITION OF FORENSIC CHEMISTRY Forensic chemistry is defined as that branch of chemistry which deals with application of chemical principles in the solution of problems that arise in connection with the administration of justice. It is chemistry applied in the elucidation of legal problems.


SCOPE OF FORENSIC CHEMISTRY : SCOPE OF FORENSIC CHEMISTRY Forensic chemistry embraces a large and diversified field. It includes not only the chemical side of criminal investigation with which it is generally associated with the public mind but also the analysis of any material the quality of which may give rise to legal proceedings.


SCOPE OF FORENSIC CHEMISTRY cont… : SCOPE OF FORENSIC CHEMISTRY cont… Forensic chemistry is not limited to purely chemical questions involved in legal proceedings. It has invaded other branches of forensic sciences notably legal medicine, ballistics, questioned documents, dactyloscopy, and photography.


SCIENTIFIC EVIDENCE : SCIENTIFIC EVIDENCE EVIDENCE: Evidence is a means, sanctioned by law, of ascertaining in a judicial proceedings the truth respecting a matter of fact. SCIENTIFIC EVIDENCE: The means sanctioned by law, of ascertaining in a judicial proceeding the truth respecting a matter of wherein scientific knowledge is necessary.


BASIC FORMS OF EVIDENCE : BASIC FORMS OF EVIDENCE Direct Evidence – that which the senses perceive. Any fact to which a witness testifies based on what he saw, heard, smelled, touched or tasted, is direct evidence. Circumstantial Evidence – a kind of evidence which seeks to establish a conclusion by inferences from proved facts.


BASIC FORMS OF EVIDENCEcont… : BASIC FORMS OF EVIDENCE cont… Hearsay evidence – a statement made by a witness on the authority of another and not from his own personal knowledge or observation.


FORMS OF SCIENTIFIC EVIDENCE : FORMS OF SCIENTIFIC EVIDENCE Real or Autoptic evidence – evidence which is addressed to the senses of the court. Testimonial evidence - comes from people. E.g. testimony of an expert witness in court


FORMS OF SCIENTIFIC EVIDENCE cont… : FORMS OF SCIENTIFIC EVIDENCE cont… Experimental evidence – An expert witness may be required to perform certain experiments to prove a certain matter of fact. Documentary evidence – any written evidence presented by an expert in court.


WITNESS : WITNESS A witness in court may be an ordinary or expert witness. As ordinary witness, the Rules of Court requires that the person must have the following qualifications: He must have the organ and power to perceive The perception gathered by his organ of sense can be imparted to others.


WITNESS cont… : WITNESS cont… He does not fall in any of the exception provided for by law. The opinion of a witness regarding a question of science, art or trade, where he is skill therein, may be received in evidence. This kind of witness is called EXPERT WITNESS.


ORDINARY WITNESS VSEXPERT WITNESS : ORDINARY WITNESS VS EXPERT WITNESS ORDINARY WITNESS can only state what his senses have perceived while EXPERT WITNESS may state what he has perceived and also give opinion, deduction or conclusions to his perception.


ORDINARY WITNESS VSEXPERT WITNESS cont… : ORDINARY WITNESS VS EXPERT WITNESS cont… An ORDINARY WITNESS may not be skilled on the line he is testifying while an EXPERT WITNESS must be skilled in the art, science or trade he is testifying.


ORDINARY WITNESS VSEXPERT WITNESS cont… : ORDINARY WITNESS VS EXPERT WITNESS cont… An ORDINARY WITNESS cannot testify on things or facts he has not perceived except those provided for by law while an EXPERT WITNESS may testify on things which he has not seen by giving his opinions, deductions or conclusions on the statement of facts.


THE PRACTICE OF FORENSIC CHEMISTRY : THE PRACTICE OF FORENSIC CHEMISTRY PRACTICE OF FC: Four Stages Collection or reception of specimen to be examined; Sufficiency of samples Standard for comparison Maintenance of individuality Labeling and sealing The actual examination; The communication of results of examination Court appearance


THE PRACTICE OF FORENSIC CHEMISTRY cont… : THE PRACTICE OF FORENSIC CHEMISTRY cont… SIX GOLDEN RULES IN THE PRACTICE OF FC Go slowly Be thorough Take notes Consult others Use Imagination Avoid complicated theories