FORENSIC 8 | Forensic Chemistry

• FORENSIC CHEMISTRY
• Brief History of Forensic Chemistry (Timeline)

  • 1858: First Medical Textbook Printed
  • 1871: Teaching of Legal Medicine
  • 1876: Creation of the position of "Medico Titulares"
  • 1884: Anacleto del Rosario as Chemist in the Committee to study mineral waters of Luzon
  • 1887: Laboratorio Municipal de Manila was created
  • 1894: Rules regulating the services of "Medico Titulares y Forences"
  • 1895: Antonio Luna established a clinical laboratory for Chemical Analysis
  • 1898: Preservation of the Spanish Forensic Medicine System by the American Civil Government
  • 1899: Establishment of the first Crime Laboratory by the US Army
  • 1901: Bureau of Government Laboratories (BGL) was created
  • 1908: Teaching Legal Medicine and Ethics in Philippine Medical Schools (UP)
  • 1915: Creation of Legal Medicine with authority to collect materials in the interest of Medico-Legal Questions
  • 1922: Department of Legal Medicine of UP became a branch of the Department of Justice
  • 1937: Creation of Division of Investigation (DI) under DOJ with Medico-Legal as part of the Division
  • 1938: Department of Legal Medicine abolished and later on turned-over to the Medico-Legal Section of DI
  • 1939: PC having its own medico-legal office with chemical laboratory
  • 1942: Creation of NBI
  • 1945: PC Crime Laboratory activated the Fingerprint Identification Unit
  • 1947: Criminal Laboratory Branch of PC (Ballistics, Photography and Fingerprint)
  • 1951: New sections added: Mobile Unit, Lie Detection Section, Physical Identification Section
  • 1959: Independent Technical Laboratory Branch (PC Forensic Laboratory)
  • Present: Two distinct Crime Laboratory in the Philippines - Forensic Chemistry Division of NBI and PNP Crime Laboratory
• Forensic Chemistry


  • Application of Chemical Principles in the examination of physical evidence
  • Chemistry applied in the explanation of legal problems
• Scope of Forensic Chemistry


  • Includes the chemical side of investigation
  • Analysis of materials leading to legal proceedings
  • Also answers questions in other aspects of Forensic Science
• Evidence


  The means, sanctioned by these rules (law), of ascertaining in judicial proceedings the truth respecting a matter of fact
• Scientific Evidence


  • The means, sanctioned by these rules (law), of ascertaining in judicial proceedings the truth respecting a matter of wherein scientific knowledge is necessary
  • Based off of knowledge that has been developed by using scientific method and is generally accepted within the scientific community
• Forms of Scientific Evidence

  • Physical Evidence
  • Testimonial Evidence
  • Experimental Evidence
  • Documentary Evidence
• Physical Evidence


  Any material items that would be present on the crime scene or the victims
• Real (or Autoptic) Evidence


  Evidence addressed to the senses of the court
• Trace Evidence


  Evidence that is found at a crime scene in small but measureable amounts
• Colin Pitchfork Case – First Criminal to be convicted of murder based on DNA evidence
• The legal system widely recognizes the role of forensic evidence in the trial of criminal offenders. This is because when scientific techniques and methods are used, there is not much scope for bias or injustice. That is why DNA profiling and a host of other forensic evidence are widely accepted in courts across the world.
• Role of Forensic Chemistry

  • Speedy investigation
  • Solution of crimes
• Chemical findings are used in

  • Convicting the guilty
  • Clearing the innocent
• Principles in the Collection of Physical Evidence

  • Adequacy/Sufficiency of standards and questioned samples
  • Integrity of samples (Markings for Identification)
  • Proof of Standard (Validity of Evidence)
• General Rules in the Collection of Evidence

  • Obtain it legally
  • Note details and description of collected evidence
  • Proper identification of evidence
  • Proper packaging, sealing and storage
  • Proper shipping/delivery to the laboratory as soon as possible
  • Maintaining Chain of Custody
• Factors Contributing to the Loss of Physical Evidence

  • Lack of Precautions preventing Tampering of Specimen
  • Failure in the Preservation
  • Failure in the Transport of Specimen
  • Failure in Identifying the Specimen
  • Improper Packaging of the Specimen
• Stages in the Work of a Forensic Chemist

  • Collection or Reception of the Specimen to be examined
  • Actual Examination of Specimen
  • Communication of Results
  • Court Appearance
• Quantitative Examination


  How much
• Methods of Analyses

  • Wet Method
  • High Precision Method
• Techniques Used in Forensic Chemistry

  • Microscopy
  • Photography
  • Invisible Rays
  • Chromatography
  • Electrophoresis
  • Spectrography
  • Laser Technique
  • Mass Spectrometry
  • Spectrophotometry
  • Neutron Activation Analysis
  • X-ray Diffraction Analysis
  • DNA Typing
  • Forensic Entomology
  • Atomic Absorption Spectrophotometry
• Characteristics of Tools and Techniques Used

  • Sensitivity
  • Specificity
  • Rapidity
• Principles Used in Forensic Chemistry

  • Law of Individuality
  • Law of Progressive Change
  • Principle of Comparison
  • Principle of Analysis
  • Law of Probability
• FORENSIC CHEMISTRY & TOXICOLOGY
• BLOOD AND BLOODSTAINS
• Importance of the Study of Blood


  • As circumstantial or corroborative evidence
  • For disputed parentage
  • Determination of the cause of death and the length of time the victim survived the attack
  • Determination of the direction of escape of the victim or the assailant
  • Determination of the origin of the flow of blood
  • Determination of the approximate time the crime was committed
• Nature of Blood

  • Largest circulating tissue of the body
  • Consists of vital substances
  • Fluid that circulates in to the Cardiovascular System
• Functions of Blood

  • Transport of gases (O2 and CO2), nutrients, and wastes
  • Regulates Body Temperature
  • Regulates pH of the body fluids
  • Transportation of injected and otherwise given medicine to the affected parts of the body
• Kinds of Blood

  • Arterial Blood
  • Venous Blood
• Characteristics of Blood

  • Color
  • Volume
  • Viscosity
  • Specific Gravity
  • pH Reaction
  • Circulating Tissue of the Body
• Factors Affecting the Amount of Blood

  • Weight
  • Age
  • Diet
• Problems in the Study of Blood

  • Where blood has to be searched for
  • Collection, preservation and transportation of specimen suspected to contain blood
  • Is the stain that of blood?
  • Does the stain contain blood or another substance?
  • Is it human or animal?
  • If the stain is of human blood, did of come from the victim, the accused or from other persons?
• Composition of Blood

  • Formed Elements
  • Liquid Portion
• Formed Elements

  • Red Blood Cells (Erythrocytes)
  • White Blood Cells (Leukocytes)
  • Platelets (Thrombocytes)
• Hemoglobin (Hb)


  • Coloring matter of blood
  • Pigment which is found in the cytoplasm of RBCs
  • Carries / Transport Oxygen
• Types of Hemoglobin

  • Abnormal Derivatives of Hb (Methemoglobin, Sulfhemoglobin, Carboxyhemoglobin)
  • Normal Hemoglobin (Oxyhemoglobin, Reduced Hemoglobin)
• Phases of Blood Examination

  • Preliminary Tests
  • Confirmatory Tests
  • Quantitative Tests
• Methemoglobin (HbM)


  Found in NO3 and NO2 poisoning, blood is chocolate brown in color
• Sulfhemoglobin (HbS)


  Found in the presence of the bacteria Clostridium perfringens & Clostridium botulinum, severe constipation, enterogenous cyanosis, blood is lavender in color
• Carboxyhemoglobin (HbCO)


  Due to excessive inhalation of gas from defective stoves and from automobiles, blood is cherry red in color