Forensic Labs

The Los Angeles County Department of Medical Examiner Forensic Sciences Laboratories Division is responsible for the identification, collection, preservation, and analysis of physical and medical evidence associated with Medical Examiner’s cases. Our mission is to conduct a comprehensive scientific investigation into the cause and manner of any death within the Medical Examiner’s jurisdiction. This is accomplished through the chemical and instrumental analysis of physical and medical evidence.

Our goal is to provide our medical examiners, families of decedents, outside investigating agencies, and the judicial system with timely, accurate, and advanced forensic analyses; and to provide expert interpretation of these analyses through testimony and deposition. The laboratories division includes the following: Toxicology, Histology, Human Genomics Unit/DNA, Scanning Electron Microscope lab (includes gunshot residue and toolmark analysis), Field Criminalistics and Evidence Control. Additionally, the Forensic Sciences Laboratories Division’s Toxicology, Drug Chemistry, Human Genomics/DNA, and Scanning Electron Microscopy (gunshot residue and toolmark analysis) testing are accredited by ANAB (ANSI National Accreditation Board) in the field of Forensic Testing per accreditation standards set forth in ISO/IEC 17025:2017, ANAB Forensic Testing & Calibration AR 3125:2019, and FBI Quality Assurance Standards for Forensic DNA Testing Laboratories: 2020. Our forensic blood alcohol testing program is licensed by the State of California (Title 17).

For more information on additional testing, interagency assists and other requests.

Our teams of specially-trained criminalists are on call 24 hours per day to respond to crime scenes for the proper documentation, collection and preservation of physical evidence.  Such scenes may include:

  1. Ligature removal: In cases where a victim has been tied and/or restricted in any fashion.
  2. Sexual assault evidence collection: In cases where rape or any sexual misconduct/assault is suspected.
  3. Entomology evidence collection: In cases where decomposition of the body has progressed to a state that insect activity is present.
  4. Excavation: In cases where decedents have been buried or skeletonized. An anthropologist will work in conjunction with the criminalist in the recovery of human remains.
  5. Physical evidence collection: In cases where trace material including hairs, fibers, vegetative matter, or stains are present on the decedent.
  6. Arson evidence collection: In cases where an accelerant may have been used to initiate a fire, the decedent’s clothing and surrounding evidence will be collected and packaged appropriately.

Criminalists in the Drug Chemistry Section analyze materials for the presence of controlled substances such as cocaine, methamphetamine, marijuana, bath salts and synthetic cannabinoids. These controlled substances may be present in powders, solid materials, liquids, plant material, mushrooms, blotter paper, baby bottles, or food items collected at a death scene.  Analyses may also include tablets, pills or drug residue collected at autopsy from decedents’ orifices, gastric and intestinal contents.  Lastly, the section examines pharmaceutical preparations in the form of tablets, capsules, injectables and transdermal patches.

Our evidence unit is responsible for maintaining the integrity and chain-of-custody for all evidence collected from Medical Examiner cases. The unit maintains evidence collected by Department personnel such as projectiles, decedent clothing, drug paraphernalia, and trace material from submission to release or final disposition. The evidence unit provides quality service to department personnel and the many law enforcement agencies within LA county and outside the county. Additionally, the unit provides education and guidance on the collection, packaging, and proper chain of custody as needed.

Gunshot Residue (GSR) originates from the discharge of a cartridge, typically from a firearm. The residue can contain particulate from the bullet jacket, if present, cartridge case, gun powder, primer, and the firearm itself. The portion of the residue that is discoverable with a scanning electron microscope fitted with an x-ray spectrometer is the primer material.

The Scanning Electron Microscopy Laboratory (SEM Lab) performs GSR Analysis on samples collected from Medical Examiner cases and offers GSR analysis to outside investigating agencies for a fee. For information on requesting GSR analysis, click Additional Laboratory Request.

This laboratory facilitates the preparation of gross tissue specimens for microscopic examination by the medical staff.  This includes hematoxylin and eosin stains, special stains, and immuno-histochemical stains.  Through the microscopic examination of tissue, our medical examiners can determine information such as:

  1. Aging of injuries or degree of injury
  2. Diagnosis of diseases, including cancers
  3. Evaluate cellular variation in tissue
  4. Identify the presence of bacterial infections/diseases, medical disorders, and toxins
  5. Detection of by-products of some drugs as seen by crystalline structures

Toolmark analysis involves the evaluation of trauma in biological material collected from decedents and the comparison of the trauma with submitted suspect tools. Analysis can include the following: reconstruction of skeletal material, macro and micro photography, measurements, and test marks. The Laboratory has conducted this type of analysis for over 30 years for Los Angeles County and has acquired an extensive reference collection in bone exhibiting a wide range of trauma. Additionally, toolmark analyses and consultation are available to agencies outside of Los Angeles County.

Using advanced instrumentation and methods, the toxicology laboratory conducts chemical and instrumental analysis on post-mortem specimens collected at autopsy to determine the extent to which drugs may have contributed to a death.  Alcohol, drugs of abuse and various pharmaceutical medications are analyzed through sensitive and specific methodologies. Evidence that may have been submitted with a case such as powders, tablets, plant material, blotter paper, liquids, food items, and/or other materials collected at a death scene can be analyzed in the laboratory using drug chemistry techniques. These analyses are requested by the medical examiner on an “as-needed” basis.

The laboratory’s experienced forensic toxicologists offer expert drug interpretation that assists the medical examiners in answering questions like:

  1. What drug was taken?
  2. How much and when was the drug taken?
  3. Did the drug contribute to the cause and/or manner of death?
  4. Was the drug use consistent with therapeutic administration, or was it abuse?
  5. If the death is due to a drug overdose, was it intentional or accidental?

The Toxicology laboratory results, in conjunction with investigative and medical reports, help medical examiners reach a final determination for the cause and manner of death.

The Human Genomics Unit conducts DNA analysis for the identification of human remains, and in 2019, will provide genetic analysis to assist our medical examiners in cause of death investigations. These services are consistent with our mission statement to inquire into and determine the circumstances, manner, and cause of all violent, sudden, or unusual deaths occurring within Los Angeles County.

While we perform kinship testing and genetic testing for our medical examiners, we do not provide paternity and maternity testing or genetic testing as a service to the relatives of a decedent. Instead, the HGU will provide a decedent’s reference sample to an outside DNA testing laboratory for a processing/handling fee at the request of the next of kin of the decedent.

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