Forensic Biology

OVERVIEW
A biological substance, such as, blood, semen, saliva, or tissue that leaves the human body and is left at the scene of a crime, may provide valuable information as to who was present at a scene and what events might have occurred. The value of this evidence can be greatly diminished if not properly collected, packaged, and preserved. In addition, due to the sensitivity of the DNA technology used by the Forensic Biology discipline, if proper precautions are not taken while collecting evidentiary samples, there is an increased likelihood of introducing contamination from a foreign DNA source unrelated to the crime. It is also possible to transfer unrelated sources of DNA between crime scene samples if the evidence is not packaged correctly.
 
PROCESSING OF EVIDENCE BY THE FORENSIC BIOLOGY SECTION
The initial examination performed by the Forensic Biology discipline is screening the evidence to identify the possible presence of a biological substance (i.e., blood or semen). Probative biological evidence can then be analyzed using a DNA technology specifically designed to test minute amounts of biological material at 24 different areas of the DNA (21 STR markers, 1 Y-STR marker and 2 gender markers). The DNA profile obtained from the “questioned” evidence is compared to the DNA profile from evidentiary known samples (victim, suspect, or elimination buccal samples) to determine if an individual is included or excluded as a possible source of the biological substance. If no suspect has been identified, the foreign DNA profile may be searched against the DNA profiles in the DNA database, CODIS, which is comprised mainly of DNA profiles from convicted offenders and individuals arrested for specific crimes (as per AS 44.41.035), to aid law enforcement in identifying a possible perpetrator.

 
What can you tell about me from my genetic profile?
STR DNA analysis can identify the gender of an individual. Other STR locations used for forensic purposes are non-coding regions and are not known to influence any individual traits. For example, the genetic profile generated cannot tell you if a person has blue eyes or brown, black hair or red, information about height and weight, etc.
 
Why does it take so long to get DNA results?
DNA analysis involves four main laboratory steps: extraction, quantification, amplification and genotyping. Samples are often processed in batches and therefore, completing the four step laboratory process for a batch of samples can take a couple of weeks, once analysis is begun. Once a genetic profile is obtained, the data must be interpreted and a report written. All of the analysts notes, interpretations and the report  must then be reviewed by a second qualified analyst. Each of these steps is detail-intensive and time consuming and may take up to several hours for a single sample. In addition, due to a backlog of cases, it may be a few months before DNA analysis begins on a case.
 
I've often heard DNA testing referred to as DNA "fingerprinting". Is DNA testing replacing fingerprints?
No. There are several reasons why DNA testing should not be thought of as a replacement for fingerprints. The term "DNA fingerprint" is somewhat misleading and genetic profile is a more appropriate term for the data generated. Identifying and developing a fingerprint for comparison is relatively inexpensive compared to processing a sample to obtain a DNA profile. Additionally, DNA testing has its limitations – for example, it cannot distinguish between DNA from identical twins. Fingerprints are needed to distinguish between such individuals.
 

Capabilities and Services
The primary function of the Forensic Biology discipline is the identification of biological material and the use of DNA analysis to determine whether the biological material could have originated from a specific individual.
 
The Forensic Biology discipline provides three types of service: biological screening of forensic casework, DNA analysis of forensic casework, and DNA analysis of offender samples. Separate scientific reports are issued for biological screening and DNA testing of forensic casework.

The laboratory also issues CODIS hit letters to notify law enforcement when there is a DNA match between samples in the DNA database. CODIS hits are investigative leads, typically identifying a potential source of biological material from crime scene evidence.

The laboratory does not routinely perform analysis on the following:
  • vomit
  • urine
  • fecal matter
  • fired casings/bullets
  • condom wrappers
  • unopened beverage containers
  • cigarette packages or unsmoked cigarettes
  • charred/burnt material
  • controlled substance cases
  • items previously examined/processed in another laboratory; to include dusting for fingerprints
  • items taken directly from a suspect in a possession case
Triage Guidelines
The following guidelines, utilized by laboratory personnel in sample selection, have proven effective, but may vary slightly on a case-by-case basis.

Sexual Assault - the number of samples analyzed will generally correlate with the number of possible assailants and/or consent partners who may be DNA contributors; typically, one questioned sample per possible foreign contributor. Known samples from the victim(s) and suspect(s), if known, are required. Known samples from consent partners are highly recommended.

Non-sexual Assault - the number of samples analyzed will generally correlate with the number of possible DNA contributors; typically, one questioned sample per possible foreign contributor. Known samples from the victim(s) and suspect(s), if known, are required.

Homicide - the number of samples analyzed will vary based on the number of potential DNA contributors and the number of items with potential probative value.
Biological Material
Body fluids such as blood, seminal fluid or saliva, or a biological substance such as hair and tissue (muscle, fetal material, etc.)
 
Contact or Touch DNA Evidence
Evidence resulting from casual contact by an individual with a surface or material. This would include primarily objects touched by an individual’s hand(s), such as gun grips, triggers, knife handles, steering wheels, etc.

Deoxyribonucleic Acid (DNA)
The genetic material found in various body tissues (muscle, fetal tissue, skin, etc.) and body fluids (semen, vaginal fluid, blood, saliva, etc.). Because an individual’s DNA is the same from cell-to-cell within the body and is different from individual-to-individual, DNA can be used to determine whether a biological substance may have been deposited by a specific individual.
 
DNA Database Collection Kit (offender kit, CODIS kit)
A kit used for the collection and preservation of statutorily mandated DNA samples (from convicted offender and arrestees) for entry in the DNA database.
 
DNA Profile
The combined results that are obtained when testing DNA at several locations on various chromosomes; from the nucleus of the cell. The DNA comprising an STR profile is inherited from both biological parents.
 
Mitochondrial DNA (mtDNA)
Mitochondria are organelles in the cell that contain their own DNA. Mitochondrial DNA (mtDNA) is different from nuclear DNA. Each mitochondrion contains a few hundred to several thousand copies of mtDNA. Mitochondrial DNA is maternally inherited, meaning maternally related close relatives will have the same mtDNA profile. Therefore, mtDNA is less discriminating than nuclear DNA STR testing. However, mtDNA testing is more likely to be successful when samples are highly degraded due to age or environmental insults.
 
Semen
A biological substance secreted by males that consists of a combination of seminal fluid and spermatozoa
 
Seminal Fluid
A biological fluid produced by males for the transport of spermatozoa. May be absent of spermatozoa in vasectomized males or males with certain medical conditions.
 
Sexual Assault Kit (SAK)
A set of items used by medical personnel for the preservation of physical evidence collected from a person, living or deceased, following an allegation or suspicion of sexual assault.
 
Spermatozoa
The male cell involved in reproduction; carries one-half of the genetic information for a new individual.

STR DNA Analysis (Nuclear DNA)
STR DNA analysis is the most widely used method in crime laboratories and is the only method currently utilized at the AK State Crime Lab. STR (Short Tandem Repeat) testing targets and amplifies specific locations in the DNA molecule. This testing can be performed to identify not only the gender of the source of the biological material but also generate a genetic profile which enables us to distinguish between two individuals with a considerable degree of confidence.

 
Wearer DNA
DNA recovered from an article of clothing in an effort to identify the wearer of the garment
 
Y-Chromosome DNA (Y-STR DNA)
Male specific DNA found in the nucleus of most cells of the body. Y-STR analysis is used to amplify locations on the Y chromosome and Y-STR data can only be obtained from male individuals. This type of DNA is inherited paternally. This type of testing may be useful when samples are mixtures of male and female DNA or when there is very little DNA from a male contributor. Y-STR testing has its limitations since close male relatives will have the same Y-STR profile.

 

Forensic Biology procedure manuals are located in a tab under the Quality Assurance section of the webpage. They can be accessed by clicking here.
Biological fluids and body fluid stains are valuable evidence which can be used to either associate a victim or suspect with a crime/crime scene or eliminate them from consideration. The most frequently encountered biological fluids are blood, seminal fluid, and saliva.

Safety Precautions
It is imperative when collecting or packaging biological evidence for submission to the laboratory that clean latex gloves be worn and changed often. Depending on the crime scene, shoe covers, gowns, masks, head covers, and safety glasses may also be appropriate. Body fluids, wet or dry, have been shown to carry disease. Dry stains may flake when disturbed or collected, sending minute particles airborne. These may be absorbed through mucus membranes (eyes, nose, mouth, etc.), open cuts, or chapped skin. Therefore, all biological materials and fluids must be handled with universal precautions. Wearing the appropriate protective clothing also helps minimize contamination of the evidence sample with your DNA.

General Collection Guidelines
All biological evidence should be air-dried prior to submission to the laboratory. Refrigerating the evidence will retard bacterial growth on wet material. However it will not stop the growth which can then lead to degradation of the biological material. The sooner the biological evidence is dried, the more likely useful information can be obtained from the evidence through DNA analysis.

Biological evidence should be packaged in paper bags or envelopes; NEVER in plastic bags.

During the collection, air-drying, or packaging of any body fluid stains, caution should be used to ensure that a stained area from an item of evidence does not come in contact with another stained or unstained area. This applies to outer surfaces and inner surfaces. For example, a shirt should not be folded or rolled so that a stain on the front contaminates any stained or unstained area on the back or inside of the shirt. A barrier, such as paper or cardboard should be placed on the inside of the shirt, as well as under and over the garment to prevent stained areas from coming in contact with each other.

When air drying articles stained with body fluids, place them on or over a piece of clean paper. Any debris which falls from the material onto the paper during the drying process will be collected when the paper is folded with the article prior to packaging, labeling and sealing.

Body fluid evidence can be contaminated by the crime scene officer's own body fluids. The perspiration on the officer’s hands may contaminate the cotton swabs used to collect the body fluids, or talking while collecting samples may spread the officer’s saliva on the evidence. To prevent such contamination protective clothing (i.e., latex gloves, gowns, masks, and head covers) should be worn while collecting the evidence. To avoid possible sample-to-sample contamination, change latex gloves (and other applicable protective wear) as necessary when collecting evidence.

When practicable, it is best to submit the entire item of evidence to the laboratory for evaluation. If an item has been swabbed by the agency, the laboratory will not analyze the item the swab was taken from for DNA analysis. Evidence (once packaged) should be submitted to the laboratory as soon as possible. Otherwise, the items should be stored in an appropriate secured storage location until submission to the laboratory is possible. To minimize degradation of DNA, evidence should not be stored in extreme humidity or at elevated temperatures. Dry, cool storage locations are best.


 
AS 44.41.035 authorizes the collection of DNA samples from persons arrested or convicted of a Crime Against A Person or a felony under AS 11 or AS 28.35. The DNA profiles from these samples are maintained by the laboratory in CODIS (the Combined DNA Index System). The CODIS database also contains DNA profiles obtained from crime scene samples, unidentified human remains, missing persons, and relatives of missing persons. The main purpose of the database is to generate investigative leads in cases where biological evidence was recovered from a crime scene.

Law enforcement and corrections officers across the state are to collect the DNA samples as buccal swabs (cheek swabs), and submit them to the laboratory for analysis. Kits designed specifically for this purpose are provided by the laboratory and can be obtained by e-mailing dps.crime.lab.web@alaska.gov.

Click here for guidance on determining who is required to give a sample.

Click here for an overview on the CODIS System and CODIS Sample eligibility.
 
CODIS Metrics as of January 2018
  Alaska National Database
Investigations Aided 727 390,584
Crime Scene Profiles in database 1857 830,184
Arrestees in database 33,121 2,984,137
Convicted Offenders in database 24,368 13,094,164

Click here to visit the FBI Laboratory's CODIS webpage.
 
The laboratory will be bringing Y-STR analysis online later in 2018. Y-STR analysis will not be performed retroactively on cases the laboratory has already completed.

Click here for a brief tutorial on Y-STR analysis.
 
Rapid DNA, or Rapid DNA analysis, is a term used to describe the fully automated (hands free) process of developing a DNA profile from a reference sample buccal (cheek) swab without human intervention. The laboratory does not currently offer this service and has no immediate plans to implement it.

Click here to visit the FBI Laboratory's webpage on Rapid DNA Analysis

Position Statements on Rapid DNA
ASCLD-Position-Statement-RAPID-DNA
NDAA-Statement-on-Use-of-Rapid-DNA-Technology-2018
SWGDAM-Position-Statement-Rapid-DNA
General DNA Related Information
Websites of Professional Organizations


Commercial Manufacturers of Laboratory Chemistries


Websites of Private Accredited DNA Laboratories

(not an all inclusive list)


Publications

 

B. Budowle, T. Moretti, A. Baumstark, D. Defenbaugh, K. Keys, Population Data on the Thirteen CODIS Core Short Tandem Repeat Loci in African Americans, U.S. Caucasians, Hispanics, Bahamians, Jamaicans, Trinidadians. Journal of Forensic Science 1999;44(6): 1277-1286.

B. Budowle, A. Chidambaram, L. Strickland, C. Beheim, G. Taft, R. Chakraborty, Population studies on three Native Alaska population groups using STR loci. Forensic Science International 129 (2002) 51-57.

Moretti, T. et.al, Population data on the expanded CODIS core STR loci for eleven populations of significance for forensic DNA analysis in the United States (2016) Forensic Science International: Genetics 25: 175 - 181.
 

Expanded Loci Genotyping and Statistical Evaluation of Three Alaskan Native Populations