Forensic Biology

Service Manual   Table of Contents

The services of the Forensic Biology section are intended to assist the criminal justice system by providing timely scientific analysis of biological evidence. When appropriately utilized, this testing has the potential to supply unbiased information to:

  • Link or eliminate a suspect with biological evidence
  • Substantiate case circumstances
  • Corroborate or refute an alibi
  • Identify a weapon used

The forensic biologist begins by evaluating the investigative information and available evidence to understand the nature of the case and the problem to be solved. Initially, items of physical evidence are examined for blood, semen, or saliva. Further analysis is guided by the investigating officer’s request, case circumstances, sample size and condition, available technology, and/or conformance to case policy.

Classification of biological evidence by conventional serology methods (ABO and polymorphic enzyme groupings) is no longer performed. DNA technology is used for individualization of biological evidence in forensic casework. Although biological evidence can be associated with an individual, it is not possible to determine the age of the sample.

Another service of the Forensic Biology section is the development of a Georgia DNA database of convicted felons as authorized by O.C.G.A. §§ 24-4-60. This database allows for the comparison of DNA profiles from casework samples to those offenders in the Georgia file. Profiles are also periodically uploaded to a national database as well. This database utilizes a FBI program known as CODIS (Combined DNA Index System). Routine searches are performed of the Georgia database as well as at the national level. This is discussed in more detail under the “CODIS” section of this document.

Cases submitted with no known suspect will be tested and appropriate data entered into the CODIS system. It should be noted although DNA testing is performed on such cases, priority is given to those cases in which a suspect is listed.

The following is an overview of the functioning and criteria used by the Forensic Biology section in the examination and testing of evidence.

The Universal Precaution is that all biological evidence (liquid or dried) must be considered as a potentially infectious biohazard. For this reason, adequate protective clothing and proper evidence handling techniques are essential. Disposable latex gloves should always be worn when collecting and packaging evidence with possible body fluid

stains. Gloves serve the dual purpose of protecting oneself from contact with potentially infectious pathogens and when appropriately changed, preventing cross-contamination of biological stains from one item to another.

DNA has the potential to identify or eliminate a person as the source of biological evidence. Known reference samples from both the victim and suspect(s) is required to initiate DNA testing. These reference samples may be in the form of liquid blood or buccal swabbings (see below). If other persons who are suspected to be involved in a crime, their known samples should be submitted when relevant. In sexual assault cases, if recent voluntary sex (within 72 hours) is indicated, a known sample from the consenting partner is also necessary.

Liquid Blood Samples

NOTE: Collect approximately 5 ml known blood in a purple stoppered tube containing EDTA.

The blood tube(s) should be adequately labeled prior to delivery to the DOFS laboratory with the full name of the person from whom the blood was collected, the date and time of collection, the name (or initials) of the person obtaining sample, and, when applicable, the name (or initials) of the investigator observing the collection. The tube(s) should be individually sealed and enclosed in packaging that is also sealed. Marking the outer package “Knowns for DNA” will ensure proper routing in the DOFS laboratory.

Blood samples should be forwarded to the laboratory at the earliest possible time following collection. When necessary, blood can be held refrigerated prior to transfer but must not be frozen. It is preferable that blood is delivered in person during working hours but can be mailed/shipped using priority delivery. The samples should be sent early in the week so that their arrival is not delayed by a weekend. Liquid blood samples must not be enclosed in the same package with other physical evidence.

Knowledge of a blood transfusion prior to collection of a known blood should be relayed to the analyst in written documentation accompanying the sample. If a person has received multiple blood transfusions, contact the assigned analyst prior to collection of a known sample. In this instance, it may be necessary to wait 90 to 120 days before collecting the known blood.

Bandages or other samples collected from a wound are not suitable for use as a known. Bloodstained clothing will be used only when the individual is deceased and adequate known blood sample cannot be obtained. However, if this clothing is unsuitable, tissue or other appropriate samples should be collected at autopsy as described later.

Buccal Swabs

Buccal swabbings are taken from the mouth and may also be collected for use as a known sample in DNA analysis. Commerical kits may be purchased by private vendors if so desired. Instructions for collection of buccal swabbings is contained in such kits and do not require special medical personnel. NOTE: Do not collect a liquid saliva sample. Gum, cigarette butts or drink containers are also not to be collected as known reference items.

Tissue and other Biological Samples from Autopsy

Samples collected at autopsy for use as knowns are dependent on the condition of the deceased. Blood or bloodstain cards is preferred but if unsuitable or unavailable, tissues (including fingernails) or other biological samples may be submitted. Closely clipped fingernails are the preferred sample for DNA analysis when a body is decomposed. Because certain tissues are unsuitable, it is recommended that the Forensic Biology section be contacted regarding the best-known sample source for analysis. These submissions must be adequately labeled with the sample type in addition to other identifying information. Samples preserved in formaldehyde (formalin) are unsuitable for DNA. Tissues should be frozen immediately to best preserve sample quality and transported to the DOFS laboratory on ice or priority shipped on dry ice.

Physical Evidence

When collecting physical evidence, it is preferable that the entire object be submitted to the laboratory with questioned stains intact. If removal or transport of an item is not possible, the stain(s) may be cut out or, when necessary, scraped from the item. Small stains should be collected on a water-dampened cotton-tipped applicator that must be air dried prior to packaging. Due to the sensitive nature of DNA testing, care must be taken not to contaminate the sample by the individual collecting the sample. This includes wearing gloves and refrain from sneezing or coughing on the sample.

Physical evidence for serological and DNA analysis should be packaged in paper, paper bags, envelopes, or cardboard boxes as appropriate to the sample type. For example, blood scrapings should be enclosed in folded paper packets, which are capable of containing the evidence without loss. Envelopes, paper bags, and pillboxes do not provide a suitable enclosure because scrapings can leak out at seams or openings. Tape is also an unsuitable method to retain scrapings. Plastic bags and airtight containers are unacceptable because they create an environment that can be damaging to biological evidence. Because heat, humidity, and sunlight all have destructive effects, evidence packages should always be maintained in a cool, dry location following collection.

Items from separate sources (victim and suspect clothing) or those suspected to have stains from different donors should always be packaged separately. These should not be handled excessively – especially in stained areas. All evidence items must be completely dried without heat or sunlight before packaging for delivery. Items with wet stains should be spread out on clear paper to dry because if they are folded wet, multiple stains can be created from one stain. Air-drying should be accomplished in a manner, which prevents cross-contamination of stains and loss of other evidence types (hair, fibers, or other trace evidence). Proper drying is particularly important to minimize the degradation of DNA.

Sexual Assault Evidence Collection Kits

The GBI Sexual Assault Evidence Collection Kit is prepared commercially. These kits have been adapted to comply with the statewide medical examination protocol developed for sexual assault victims. The kit is sufficient to collect adequate samples from the victim’s body to perform semen testing through DNA analysis. The instruction sheet provided in each kit is explicit and complete for proper evidence collection. Inadequate collection and/or preservation of these samples can eliminate the potential for suspect identification. No tubes are provided to obtain a known blood sample from the victim during the medical examination. In 2003 these kits were produced to include envelopes and swabs to collect buccal swabs as a known reference sample. If blood samples are taken, they should not be placed inside the sexual assault kit itself and should be packaged separately as described above.

When adequate known blood from victim and/or suspect is submitted and reasonable justification accompanies the service request, evidence will be examined to:

  • Locate bloodstain(s)
  • Identify blood by chemical testing
  • Determine if of human origin (this is not done if sample is to be DNA tested)
  • Perform DNA testing

Bloodstains from a victim’s clothing or from under the body will not be profiled when there is no question as to the blood’s source. This request deviates from the basic premise of establishing a transfer between the victim, suspect, object, or location. For the same reason, multiple bloodstains collected from a crime scene will not be classified unless there is justifiable reason to expect that the suspect is bleeding. The fewest possible number of samples will be examined to answer the question at hand. Weapons removed from a wound by medical or autopsy personnel will not be routinely examined for blood.

When evidence is submitted in a sexual assault case with a suspect identified, the evidence will be examined as appropriate to:

  • Locate semen stain visually or by alternate light source
  • Examine microscopically for spermatozoa (sperm)
  • Test for other semen components when negative for sperm
  • Perform DNA typing when requested

NOTE: Liquid semen is not needed as a known sample.

When a sexual assault evidence kit is submitted with no suspect identified, the items will be examined for semen. DNA analysis will be performed on cases that are positive for spermatozoa. The male DNA fraction from sexual assault cases will be entered into CODIS for comparison with other cases as long as it is of probative value.

Sexual assault evidence collection kits are examined as initial priority.
Victim’s clothing and bed linen will not be routinely examined for semen. An investigator may request this service by providing information which warrants the examination or indicates the likelihood that semen would be found there when not present in swabbings from the victim’s body or a sexual assault kit was not taken. Proper collection of victim’s clothing remains important, however, because it can be needed for DNA analysis in some circumstance.

Semen identification is not performed on suspect’s clothing or bed linen.

When dried stains or questioned samples are submitted, the evidence items will be examined to:

  • Locate stain(s) using alternate light source
  • Identify amylase (a chemical component of saliva)
  • Evaluate suitability of evidence for DNA analysis
  • Perform DNA typing when requested

When cigarette butts are submitted for saliva testing, the investigator must identify the brand(s) smoked by the victim, suspect, or other participants and confirm the last cleaning time of the location where collected. The examination for saliva and/or DNA typing will not be initiated until this information is provided to the analyst.

Tissue

Tissue (skin, muscle, etc.), or other body parts are identified in conjunction with the DOFS Pathology Section. Further individualization procedures are dependent on the nature and condition of the evidentiary material.

Fingernail Scrapings

When a victim indicates vigorously scratching an attacker, the fingernails may be examined for visible bloodstains or small clumps of tissue. If seen, these should be collected using sharp tweezers or other clean instrument appropriate for removing the sample. If sufficiently long, the fingernail(s) can be clipped to collect the evidence. Some artificial fingernails may require scraping if they cannot be cut. NOTE: This is typically a “last resort” avenue of testing as in most instances the DNA profile obtained is from the individual the sample was taken.

DNA typing can be used as an investigative or trial tool to:

  • Identify the donor of biological evidence
  • Exclude a falsely accused suspect
  • Associate serial rapes or other series of similar crimes
  • Distinguish multiple assailants in rape cases
  • Determine victim identity when other identification is not available
  • Determine parentage in criminal cases only (it is recommended to call the forensic biology section to discuss this service prior to submission of samples.)

DNA testing may be performed on hair if specific criteria are met. If any other probative forensic results are available, DNA testing on hair will not be performed. For questions regarding this service call the forensic biology section for further information.

CODIS is not a service per se but is a function of the Forensic Biology Section. It is a database of DNA profiles. These profiles include casework and convicted offenders. Each state that contributes data to CODIS has its own definition of who is a convicted offender. The casework is composed of “forensic unknowns”, which is predominately sperm DNA profiles from sexual assault cases and blood profiles from homicide, burglary, and assault cases. The FBI provides CODIS service and its software. Approved states may upload their profiles to the National Database to be searched against other unknown profiles and convicted felons.

Any DNA recovered from evidence submitted to the GBI that did not originate from the victim or elimination person is uploaded and searched in CODIS. If a hit is made between cases, all the officers involved will be notified and advised of any needed action on their part. If a hit is made with a convicted felon, the officer will be notified to submit a new blood sample of the convicted felon for confirmation. All DNA profiles in CODIS are continuously searched against all new profiles added. Therefore there is no need to request a search in CODIS.

CODIS does not allow the users to upload profiles of victims, suspects, and elimination blood samples (e.g. DNA profiles of consensual partners in sexual assault investigations).

The completion time for serological testing is highly variable and dependent on number and types of evidence items. The examination time for a single item is estimated below:

  • Human blood – several hours to overnight
  • Semen – several hours to overnight
  • Spermatozoa (sperm) – several hours
  • Saliva – one day (includes overnight)

The longer time is usually needed when initial examinations are negative and require more extensive testing. Examination of multiple items will also increase these times significantly.

DNA analysis has a designated protocol which cannot be “rushed”. The documentation and attention required by the procedures are essential to its success. Testing takes two weeks. Refer to “Collection and Submission of Known Samples” for these requirements.