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Understanding Serology and Biological Evidence | Criminal Defense and DNA | Fresno, Ca (1)

Posted by Jonathan Rooker | Oct 04, 2017 | 0 Comments

Understanding Serology and Biological Evidence | Criminal Defense and DNA | Fresno, Ca (1)

What is Forensic Science?

Forensic Science can be defined as the application of science as it pertains to the law. The basic tenet of forensic science is based on the observations by French doctor and forensic pioneer, Edmond Locard (1877-1966), who recognized that when two objects came into contact that there was a bi- directional transfer of material between the two objects. His observations became known as the Locard Exchange Principle; widely quoted as “Every contact leaves a trace”.

The type of evidence Locard was referring to is commonly known to us as Trace Evidence and includes evidence such as latent prints, hair and fiber and soil evidence, left behind when and where two objects have come into contact.

Over the last century, the field of Forensic Science has evolved into many distinct specialties with disciplines that range from Forensic Toxicology, Forensic Biology/Forensic Serology, Ballistics and Crime Scene Investigation to Forensic Meterology and Forensic Engineering.

Once its own forensic discipline, Forensic Serology is now sometimes referred to, by some agencies, as Forensic Biology since the development of DNA testing superseded the traditional serological techniques of personal identification. Adopting ASCLD-LAB terminology many labs are again renaming their Forensic Biology sections as Forensic Serology. For this reason and for the purposes of this course, we will use the terms Forensic Serology and Forensic Serologist.

Forensic Serology is best described as the investigation and analysis of biological evidence, such as blood and other bodily fluids and tissue, as a means of identification and reconstruction of crime scenes. In 1901 Karl Landsteiner first observed the agglutination of human blood cells with human sera and determined that blood could be distinguished by a specific group or type, leading to the development of the classic ABO blood grouping system we still use today. From identification using blood grouping the discipline has further evolved into the more discriminating application of forensic DNA testing. 

Historical Overview of Forensic Serology


First attempts were made to identify reddish brown stains on clothing as blood, using microscopy and chemical tests for the presence of hemoglobin; these were the first presumptive tests developed for blood identification



The first confirmatory test for hemoglobin was developed

Ludwig Teichman (Poland)


A method for distinguishing between animal and human protein was first published in the scientific literature

Paul Theodor Uhlenhuth



Differences were identified between human blood types that formed the basis for ABO blood types; agglutinins were identified

Karl Landsteiner (Austria)


Methods were developed for grouping dried blood stains

Leones Lattes ( Italy)


Rhesus blood factors were identified

Landsteiner and Weiner


The Ouchterlony species identification test was developed

A. Ouchterlony (Sweden)


Tests were developed for species identification using mixed agglutination methods

Stuart S. Kind (UK)


Polymorphic variants of the phosphoglucomutase (PGM)

enzyme system were identified

Brain Culliford (UK)


Further research determines that polymorphic variants exist for a number of serum proteins and blood enzymes



Seminal work in DNA fingerprinting was first published in the scientific literature

Alex Jefferies


DNA profiling applied to the forensic case and the identification of Colin Pitchfork



The polymerase chain reaction (PCR) techniques was invented

Kary Banks Mullis


FBI begins using DNA analysis in casework



The National Research Council publishes its first report (NRC I) DNA Technology in Forensic Science



The first STR it becomes available



The National Research Council publishes its second report (NRC II) The Evaluation of DNA Evidence



FBI establishes CODIS DNA database



DNA Advisory Board (DAB) establishes quality assurance standards for forensic DNA laboratories.


Crime Scene Investigation

Blood and other biological fluids may be recovered as evidence in violent crimes. This evidence is commonly found as blood from the victim on the clothing of an assailant, as semen from an assailant recovered from a rape victim, or perhaps as a series of blood spatters left at a crime scene. Less obvious forms of evidence include body fluids such as saliva, urine, vomit, and amniotic fluid; body parts, human remains, and tissues associated with mass disasters and homicides, as well as injuries inflicted in vehicular hit and run accidents. Although such samples contain markers of individuality, the individualizing tests may be hampered by sample degradation; the occurrence of mixed fluids; poor sample integrity, and the challenges of analyzing samples mixed with chemicals, textiles and dirt.

It is the responsibility of the forensic serologist to determine the characteristics of recovered blood, to perform identification as well as bloodstain and blood spatter examination, and to present their findings as an expert witness in a court of law. The forensic serologist also analyzes semen, saliva, and other body fluids and may include DNA typing as one of their individualizing techniques.

Principles of Crime Scene Investigation

The forensic serologist can encounter a vast array of physical and biological evidence in the laboratory and in some cases may be called to help or guide the collection and interpretation of evidence at a crime scene. Successful and meaningful evidence analysis in the laboratory depends on a thorough investigation of the crime scene and the appropriate collection and preservation of the biological evidence.

Some of the most important aspects of crime scene investigation include:

  • securing the scene
  • the prevention of contamination
  • the preservation of physical evidence
 Securing the Scene

Personnel responding to a crime scene must enter the scene with caution and be cognizant of other personnel, vehicles, ongoing events, potential evidence, and environmental conditions. Initial observations such as the presence of distinctive odors or sounds may be of use at a later time in the investigation. In some circumstances there may be a secondary crime scene or multiple crime scenes to investigate and process. On arrival at the scene the forensic investigator should assess the site and consider any safety measures that need to be taken to protect themselves and other personnel.

Securing the crime scene area is the responsibility of the initial responding officer (IRO). The IRO identifies anyone present at the scene, and takes appropriate steps to prevent the alteration or destruction of physical evidence by restricting movement and scene activity. Establishing, defining, and controlling the boundaries of the scene facilitates the maximum preservation of evidence. These boundaries are determined by the location of the scene and the type of crime committed.

As a general rule, boundaries start at the center of the scene and extend outward to include:

  • Where the crime occurred
  • Potential points of entry and exit of suspects and witnesses
  • Places where the victim or evidence may have been moved

Boundaries are critical for the control of evidence integrity and can be created by setting up physical barriers, by controlling the flow of personnel into and out of the scene, documenting the entry of persons entering or leaving the scene, and preventing the loss, or compromise of evidence from the effects of weather, foot traffic and vehicular damage.

Processing the Scene

The first step in any routine crime scene investigation is to establish a plan of action and a crime scene reporting protocol. A basic protocol for scene processing is summarized below:

  • Surveying the scene
  • Photographing and searching the scene
  • Mapping and measuring the scene
  • Recording and documenting the location of physical evidence at the crime scene
  • Searching for fingerprints and other physical evidence

The forensic analyst attending the scene may be involved in surveying, searching, recording, and the recovery of evidence. The investigator must approach each scene in an organized and routine manner, conducting carefully executed searches to facilitate the preservation of fragile evidence and to identify and obtain the most useful evidence present.

Recording the Scene

All activities and observations made at a scene, must be documented to preserve the events and information.

Documentation may take the form of sketches, written notes, photography and video. Documentation ensures the integrity of the investigation and provides a permanent record of the scene for later evaluation. Records include observations such as the location of persons, vehicles, or items within the scene, and the condition and appearance of the scene upon arrival.

Most records are made by the investigator in charge, and scene processing personnel during the scene walk -through.  A walkway other than the established path of entry should be used to reduce contamination.

Information can be recorded on preprinted documents or forms designed for recording different aspects of crime scene investigation. Many of these documents, which may also be used in the laboratory as part of the note taking and searching part of evidence analysis, have been developed and refined from years of actual case experiences. The design of the document may vary, but the purpose and goals behind their use are identical from one agency to another. These templates may include body outlines for recording injuries, clothing outlines for recording damage or staining, and data analyses sheets for the simple recording, reference to, and interpretation of, basic laboratory and presumptive tests.

Identification, Collection, and Preservation of Evidence

During the walk -through, fragile and perishable evidence should be identified and protected. This evidence should then be documented, photographed and collected.

During processing of a crime scene, contamination is controlled by limiting access to those directly involved in scene processing. Specific areas should be designated for trash and equipment, and single-use materials should be used for the collection of biological materials and other trace evidence, to minimize cross contamination.

The collection of evidence should be prioritized to minimize loss and contamination. At a crime scene a secure area is generally identified for the temporary storage of evidence in accordance with rules of evidence, and a chain of custody is established. A systematic search pattern, usually determined by the size and nature of the scene, is used for the location and collection of evidence. Several different search patterns may be used depending on the nature of the crime scene being processed:

  • Strip or lane search
  • Grid search
  • Spiral search
  • Quadrant search

As an example, spiral searches are generally used in underwater crime scenes. The search will begin where the key evidence (such as a body) is located and radiate and extend outwards in a spiral pattern.

The way physical evidence is handled is one of the most important factors of an investigation. The collection of evidence must be documented, and should include records of its location at the scene, the date of collection, and who collected it, as part of the chain of custody. During evidence collection the investigator also ensures that appropriate reference and standard materials (controls) are obtained from the scene for comparison purposes. Once the scene has been processed, a final walkthrough is conducted to ensure that all evidence has been collected and that materials are not inadvertently left behind.


Go to http://www.crime  for an overview of the evidence collection guidelines for the following types of evidence that are routinely recovered in serology/biology forensic cases:

  • Bloodstains
  • Seminal stains
  • Hair
  • Fibers

Human Remains and Identification

In a homicide investigation, the forensic investigator has a responsibility to help establish the nature of death; whether it is accidental, homicide or suicide, while preserving any evidence that's present at the scene. Moving the body, clothing, or any other items covering a corpse may result in the loss of evidence.

Notes taken at this type of scene should include the following details:

  • Position of the body
  • Description and state of clothing (is it partially removed, stained, tangled or twisted?)
  • Describe the location, intensity, size, direction of flow (if possible) of any staining
  • Type of stain (blood-like, semen, dirt, vomit, feces, urine or some other fluid
  • Any visible damage to the clothing and body
  • Description of blood staining (spots, spatter, or smearing and directionality)
  • Appearance of evidence removal (has the body been washed or blood cleaned from the body?)
  • Estimated amounts of blood (has staining penetrated layers, carpeting or other surfaces, is it superficial?)

A corpse that is located outdoors, or that has apparently been moved from another location, warrants some special consideration since the remains may be partially decomposed or damaged by insects or animals, or crucial evidence may be lost at the original location. As before, the careful examination and application of standard procedures for maximum crime scene and evidence protection should be applied to the collection of evidence that includes trace evidence and body fluids.

The recovery and analysis of human remains is a complex process since the body may have been subject to a large degree of decomposition and alteration. Some skeletal parts and some organs may remain, which together with clothing fragments, may provide useful evidence. Human remains are found in a variety of places including outdoors, but also, in attics, furnaces, and basements. A body may have been buried in soil, frozen, covered with brush or overgrown vegetation. With the recovery of outdoor remains, clothing and evidence may be spread over a wide area and may have been subjected to animal interference and insect infestation. With appropriate care and procedures, all of these scenarios can still provide large amounts of evidence.

Estimating Time of Death

In murder, accident, and suicide cases, the time of death is an important detail for the investigation. Using post mortem changes in the body, an approximate time can often be determined. The following parameters are usually given consideration:

  • Changes in the eyes such as dulling of the cornea and the appearance of a film
  • Body temperature cooling that can be related to the outdoor conditions
  • The temperature of the body at the time of death
  • Whether the body is clothed or unclothed
  • The presence of rigor mortis
  • The presence of post mortem lividity
  • Degree of decomposition

Algor Mortis is the cooling of the body after death when the ambient temperature is cooler than the body temperature. A nearly nude body will generally cool at a rate of 1.5 0C per hour, for the first 8 hours, when the ambient temp is 18-200C.  Many factors can cause a body to deviate from 370C plus environmental conditions such as heat cold, burial etc all affect cooling rate too.  A body usually reaches ambient temperature 18 to 20 hours after death. Rigor Mortis is rigidity that appears 6 to 12 hours after death due to biochemical changes in the muscle tissue. The degree and extent of rigidity can be used to estimate time of death. Rigidity remains for 2 to 3 days then disappears again. When blood circulation stops, blood pools in the lower extremities of the body due to the effects of gravity, causing a purplish red appearance called Livor Mortis. Lividity appears 1 hour after death and is fully developed within 3 to 4 hours. The location of lividity on the body can also be used to determine whether a body has been moved from its original position.

Putrefaction is the breakdown of the body due to autolysis and bacterial decomposition. These events convert tissues of the body into liquids and gas that cause discoloration, bloating, and swelling. Within a short period of time, fluid filled blisters appear on the skin, and the pressure of internal gases can force stomach contents out of the mouth, nose and anus. Although submersion in water results in similar effects, the processes are generally slowed due to colder temperatures. Microorganisms present in soil also decompose buried bodies. Within one to 3 years, all soft tissues will have disappeared leaving only bones. Bodies may be preserved by mummification or through the formation of adipocere, a waxy covering which begins to develop in 6 to 8 weeks as body fats are hydrolyzed.

Crime Scene Analysis

Use of Crime Scene Photography

Crime scene photographs are permanent pieces of evidence that may be presented in a court of law to prove or disprove facts or issues in question. Although an investigator can verbally describe a crime scene, photographs can be used to present the same facts in a more accurate and easily understood way. Photographs can be a useful record of blood distribution or spatter patterns for easy reference back at the laboratory.

Bloodstain Interpretation

Blood evidence can provide information that may be used to solve a case, so correct documentation, collection, and preservation of blood evidence is very important since improper handing can destroy its evidentiary value. Properly collected and preserved blood evidence may be used to link an individual to a criminal act or a crime scene; to strengthen or contradict a witness or suspect's statement, or to eliminate a person as a potential criminal suspect. Properly documented, collected, and stored blood evidence can be presented in a court of law several years from the time of the criminal act.

Bloodstain Pattern Analysis

The shape, appearance and distribution of blood drops at a crime scene may be used to reconstruct a crime. The shape and appearance of bloodstains and smears on clothing or other surfaces may also provide useful information about a crime.

Vehicles as Crime Scenes

A vehicle used for a murder or to transport a victim may hold an array of physical evidence. In some cases the victim may still be present in the vehicle, or the victim may have been removed. The procedures for searching in these scenarios are the same as those at any other crime scene. Care should be taken with the vehicle interior as limited space for working may cause physical and trace evidence to be lost or destroyed.

Hit and Run Investigations

In hit and run cases there are two types of scenes to process:

  • Damage to other vehicles or property
  • Death and injury

Physical evidence can exist which may -

  • Identify the missing vehicle
  • Connect the vehicle with the crime scene or the victim
  • Help in reconstructing the events surrounding the crime

Types of evidence that may associate a vehicle with a scene or victim include:

  1. Hairs
    2. Clothing fibers
    3. Paint
    4. Glass
    5. Blood
    6. Tissue

Crime Scene Safety

When processing a scene, or conducting a laboratory investigation, an investigator may face a number of potentially hazardous situations. Investigators routinely handle potentially biohazardous materials and chemical agents through the collection, processing, and examination of evidence. Although the investigator is ultimately responsible for recognizing chemical, biological, and physical hazards, it is the responsibility of their organization to develop policies and programs on health and safety practices; to provide training on the application of these principles, and to ensure these practices are followed. In this course we will mainly consider exposure to blood borne pathogens. However, some of the analytical techniques employed by the serologist may result in or risk exposure to toxic chemicals.

Routes of Exposure

The most common hazard faced by the forensic serologist is exposure to potentially infectious human blood and body fluids. There are several routes of exposure to biological and chemical hazards to be aware of:

Inhalation of airborne pathogens (anthrax) and volatile chemicals

Skin Contact - a frequent route of entry into the body for chemicals and biological hazards. Chemicals can cause local irritation, redness, swelling, burning or damage to the contact tissues. Severity of the reaction depends on the type and concentration of the chemical, and duration of exposure. Systemic effects can be as minor as dizziness and nausea, and as extreme as organ damage, shock, and unconsciousness.

Ingestion - Ingested corrosive materials can damage the mouth, throat, and digestive tract. Ingested toxic chemicals are usually absorbed by the body via the stomach and intestines. Regular hand washing, and abolishing the consumption or presence of food or drink in contamination prone areas, will minimize exposure to chemicals or biological contaminants by this route.

Injection - Needle sticks and mechanical injuries from contaminated glass, metal, or other sharp objects can introduce biological contaminants directly into the bloodstream.

Biological Hazards

A forensic investigator routinely comes into contact with body fluids, tissues, and biological specimens that may be contaminated with blood borne pathogens. Pathogens passed on from biohazardous materials and waste can cause life threatening and debilitating diseases such as HIV, AIDS, and hepatitis (inflammation of the liver).

Blood Borne Pathogen Safety

In 1991, the Occupational Safety and Health Administration (OSHA) issued Title 29, part 1910.1030 of the Code of Federal Regulations (CFR), Occupational Exposure to Blood borne Pathogens (BBP). Occupations considered being at risk included including law enforcement, emergency response, and forensic laboratory personnel.

Universal Precautions

Universal precautions are the fundamental mechanisms considered necessary to maintain the BBP standard and are the primary mechanisms for infection control. The BBP standard directs employees to treat all human blood, body fluids, or other potentially infectious materials as if infected with hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV).

A number of protective measures should be taken to avoid direct contact with these potentially infectious materials:

  • Barrier protection - disposable gloves, coveralls, and shoe covers must be worn when handling potentially infectious materials.
  • Appropriate eye and face protection - worn to protect against splashes, sprays, and spatters of infectious materials.
  • Similar precautions may be followed when collecting dried bloodstains.
  • Place contaminated sharps in closable, leak proof, puncture-resistant containers when transported or discarded. Label the containers with a Biohazard warning label.
  • Prohibit eating, drinking, or applying cosmetics where human blood, body fluids, or other potentially infectious materials are present.
  • Well-fitting respirators can be worn when there is potential for contamination or transfer from airborne biohazards.
Proper Handling of Biohazardous Waste

Contamination and Transfer

Processing crime scene evidence can generate substantial amounts of waste that is a potential contamination risk. Any instruments that are used in the collection and processing of evidence may become contaminated with biohazardous tissues or fluids. Equipment can be decontaminated after use with a solution of household bleach diluted 1:10, 70 percent isopropyl alcohol, or other disinfectant.

For an article on the types of biohazardous waste generated at a crime scene, and decontamination procedures go to

Biological Waste

Biohazardous waste or regulated medical waste (RMW) (infectious waste) storage and disposal procedures are highly regulated. Regulated medical waste is any waste that is capable of producing an infectious disease by an organism likely to be pathogenic to healthy humans. Cadaver waste, human blood, body fluids and tissues are considered to be RMW and require specialized handling, labeling, storage and disposal. RMW should not be mixed with regular lab waste and should be contained in specially color-coded waste containers with appropriate biohazard labeling.

Personal Protective Equipment (PPE)

Hand Protection
Gloves should be selected on the basis of the type of material being handled and the hazard or hazards associated with the material. Gloves should be constantly checked for tears or holes before and during wear. Care should also be taken to minimize contamination to other surfaces while wearing gloves. They may be protecting you but don't open a door or answer the phone while wearing gloves as you may leave behind residues that could infect other people.

Eye Protection
Safety glasses and goggles, should be worn when handling biological, chemical, and radioactive materials. Face shields give better protection to the face when there is a potential for splashing. Protective eyewear should also be worn over prescription glasses.

Foot Protection
Shoes that completely cover and protect the foot are required. Protective footwear should be used at crime scenes when there is a danger of foot injuries due to falling objects or to objects piercing the sole and when there is a risk of electrical hazards. In some situations, shoe covers can provide barrier protection to shoes and prevent contamination outside of the crime scene.

Respiratory Protection
Certain crime scenes, such as bombings and clandestine laboratories, can produce noxious fumes and other airborne contaminants that make respiratory protection necessary. Some of the organic solvents used routinely in clandestine labs can also be absorbed through the skin.

Laboratory Safety

Laboratory Safety Equipment
Many chemical and biological processes conducted in the laboratory can be carried out with the use of a ventilated fume hood. These hoods have an extractor fan that sucks the fumes or hazard away from the technician and vents it to a safe area.

Special Consideration - Mass Disaster

When a mass disaster occurs, the scene has to be processed like any other scene. Unlike smaller crime scenes, a disaster scene can be spread out over a huge area, possibly covering hundreds of square miles, so contamination and safety issues may be more difficult to control. However, the same safety precautions must be taken. Crime scene investigators are open to the same classes of hazards as at any other scene: biohazards, chemical hazards, and physical hazards. An excellent example of the hazards an investigator may encounter, and related safety procedures, are those implemented during the investigation of the ValuJet air crash in the Florida everglades. For more information read the following article at http://www.crime

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About the Author

Jonathan Rooker

Fresno DUI Attorney & Criminal Defense Attorney Jonathan Rooker is an experienced and aggressive attorney. His education and work ethic help him separate himself from the other attorneys. He provides quality legal defense at an affordable rate.


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