Dr. Henry C. Lee
Director, Connecticut State Forensic Laboratory
Professor, Forensic Science, University of New Haven

× Ø × Ø × Ø × Ø × Ø × Ø × Ø × Ø × Ø × Ø × Ø × Ø × Ø × Ø × Ø

I. Introduction

There are hundreds of varieties of physical evidence commonly submitted for examination to forensic science laboratories by law enforcement agencies. Evidence that could be subjected to DNA analysis is generally limited to things that are biological in nature. The following is a list of biological materials from which DNA has been successfully isolated and analyzed:

• Blood and bloodstains
• Semen and seminal stains
• Tissues and cells
• Bones and organs
• Hairs with follicles
• Urine and saliva (with nucleated cells)
  

Other types of biological evidence, such as tears, perspiration, serum and other body fluids without nucleated cells are not amenable to DNA analysis.

The six different types of biological evidence listed above can be used to link a person to another individual, to an object, or to a location. These types of evidence could also be used to associate or to disassociate an individual with a crime. Biological evidence is generally transferred by one of two means: direct or secondary.

Blood, semen, body tissue, bone, hair, urine and saliva can be transferred to an individual’s body or clothing, or to an object or crime scene directly. Once liquid biological specimens have been deposited, they become stains and adhere to the surface or the substratum. Non-fluid biological evidence, such as tissue, bone or hair, can also be transferred by direct contact and deposit. Direct deposit and transfer could result from any of the following situations:

• Suspect’s DNA deposited on victim (body or clothing)
• Suspect’s DNA deposited on an object
• Suspect’s DNA deposited at a location
• Victim’s DNA deposited on suspect (body or clothing)
• Victim’s DNA deposited on an object
• Victim’s DNA deposited at a location
• Witness’ DNA deposited on victim or suspect
• Witness’ DNA deposited on an object
• Witness’ DNA deposited at a location

2. Secondary Transfer

Blood, semen, body tissue, hair, saliva or urine could be transferred to a victim, suspect, witness, object or location through an intermediate medium. In a secondary transfer, there is no direct contact between the original source (donor of the DNA evidence) and the target surface. The transfer intermediary could be a person, object or a location. A secondary transfer does not necessarily furnish positive proof of a direct link of an individual with a specific crime.

The ability to perform successful DNA analysis on biological evidence recovered from a crime scene depends very much on what kinds of specimens were collected and how they were preserved. Thus, the technique used to collect and document such evidence, the quantity and type of evidence that should be collected, the way the evidence should be handled and packaged, and how the evidence should be preserved, are some of the critical points for a forensic DNA testing program. Unless the evidence is properly documented, collected, packaged and preserved, it will not meet the legal and scientific requirements for admissibility into a court of law. If the DNA evidence is not properly documented prior to collection, its origin can be questioned. If it is not properly collected, its biological activity may be lost. If it is improperly packaged, cross contamination might occur. And if the DNA evidence is not properly preserved, decomposition and deterioration may well occur. Any of these effects will seriously affect the outcome of DNA typing. The following are general guidelines for the documentation, collection, packaging and preservation of DNA evidence.

The initial stages in physical evidence examination encompass activities that take place at a crime scene as well as at the forensic laboratory. Documentation is important from two points of view in forensic science: the legal one, and the scientific one. Nothing should ever be altered until its original condition and position have been recorded. Several different means of documentation are available. Generally, the use of more than one method is recommended. Every major piece of evidence should be documented.

1. Photograph and/or videotape the evidence before touching, moving or collecting it.
2. Note the location and condition of the evidence.
3. Note and sketch the spatial relationships of the evidence relative to the crime scene and other objects present.
4. Note and sketch the condition of the biological evidence.

1. Note the package, label, seal condition and exhibits.
2. Initial the package with unique identification markings, lab case number, and date.
3. Check the exhibit number and compare with the submission form to insure that the correct item is being received.
4. Note, sketch and/or photograph the contents of the evidence item.
5. Check the item against the submission form to insure that the description of the item is correct.
6. Photograph, sketch and/or note the location and condition of biological evidence prior to any sampling.
7. If any preliminary testing is done, record the nature of the test and the results obtained. Always wear clean gloves to avoid any contamination.

Once the biological evidence is transferred through direct or secondary transfer, it will remain on the target surface either by absorption or by adherence. In general, liquid biological evidence will be absorbed, while solid state evidence will adhere. The method of collection depends largely on the state and condition of the biological evidence. The following are general guidelines for the collection of biological evidence for DNA analysis.

1. Blood and Bloodstains

1. Liquid blood from a person should be collected by qualified medical personnel.
2. Two tubes of blood, about 5 mL each, should be collected in vacutainers with EDTA as anticoagulant.
3. Each tube should be labeled with the date, time, subject’s name, location, collector’s name, case number and exhibit number.
4. Blood samples must be refrigerated (NOT frozen), and submitted to the laboratory as soon as possible.

1. Liquid blood should be collected with a clean (preferably sterile) syringe or disposable pipette and transferred to a clean (preferably sterile) test tube.
2. A blood clot can be transferred to a clean test tube with a clean spatula.
3. A clean cotton cloth can be used to soak up liquid blood or a blood clot (avoiding areas containing only serum).
4. Label the specimens with case number, item number, date, time, location, and evidence collector’s name.
5. Wet blood samples, if they are collected, must be preserved in a suitable anticoagulant and kept in a refrigerator. These specimens should be submitted to the laboratory as soon as possible.

1. Blood samples found on snow or in water should be collected immediately to avoid further dilution.
2. The largest possible quantity of these samples should be collected in a clean, suitable container, avoiding any contaminant as much as possible.
3. Label the specimens as previously indicated.
4. Freeze these specimens if possible.
5. Submit specimens to the laboratory as soon as possible.

1. Garments bearing wet bloodstains should be placed on a clean surface and allowed to air dry.
2. Never collect a wet garment or garment with a wet bloodstain in a sealed, airtight container or plastic bag. This practice causes the specimens to retain moisture, and promotes bacterial growth and sample deterioration.
3. Once the garments and stains are dry, package in a paper container with proper labeling.

Objects with Wet Bloodstains

1. Small objects bearing wet bloodstains should be allowed to air dry, then collected as is.
2. An effort should be made to preserve the integrity of any bloodstain patterns during packaging and transportation.
3. Large objects that cannot be removed from a crime scene may have wet bloodstains on them. The wet blood should be transferred onto clean cotton cloth.
4. Bloodstained cotton cloth must be allowed to air dry before packaging in a paper container.
5. Each object and container must be properly labeled.

1. Dried bloodstains on weapons, garments and other movable objects should be collected separately by collecting the entire item.
2. Each item should be placed in its own (paper) container, and these should be sealed and labeled properly.

1. The bloodstain pattern should be documented and sketched to the extent necessary.
2. The stain can be tape lifted or scraped off the object onto a clean piece of paper.
3. The tape lifter or the paper with blood crust can then placed into a "druggist fold", and placed in an envelope which is sealed.
4. Each item must be labeled properly.

1. Document and sketch the bloodstain pattern as necessary.
2. The bloodstain may be eluted onto a clean switch, moistened with sterilized saline (or water) by rubbing the cotton switch on the stained area.
3. The switch is then allowed to dry and is placed in a paper fold packet.
4. The packet is then placed in an envelope which is sealed, and properly labeled.
5. Always obtain a control by repeating the procedure on an adjacent but unstained area of the surface containing the bloodstain.

Dried Bloodstains on Carpet, Upholstery, or Other Objects that Can Be Cut

1. The stained area should be documented as previously described.
2. A portion of the item containing the bloodstain can be removed by cutting with a clean, sharp instrument.
3. Each cutting should be packaged separately and labeled accordingly.
4. An unstained portion of the item should be collected and packaged as a control.

1. Small blood spatters are often difficult to remove from their surfaces. It may be possible to collect them using the tape lift method.
2. After proper documentation, clean fingerprint tape can be used to lift the blood spatter from its surface.
3. Each piece of tape should be packaged and labeled properly.
4. Each piece of tape is placed into a larger plastic container. The ends of the tape lift should be taped in place to secure the lift.
5. Suspend the tape with the blood spatter portion in the middle of the container.
6. Seal and label the container appropriately.

1. Document the semen evidence by notes, photography, videotape and sketching.
2. Use a clean syringe or disposable pipette to transfer liquid semen to a clean, sterile test tube.
3. Label the tube with the case and item number, date, time, location, and name of the collector.
4. Keep the specimen refrigerated and submit to the laboratory as soon as possible.
5. Alternatively, liquid semen can be transferred onto clean cotton cloth by absorption. The cloth is then air dried, packaged, sealed and labeled properly.

1. Seminal stains on panties, clothing, bedsheets, pillows and other movable objects should be collected as is.
2. If an article has a wet stain on it, the stain must be allowed to air dry thoroughly prior to collection of the article.
3. Each item should be packaged separately in a clean paper container.
4. Each item’s packaging must be properly sealed and labeled.
5. Packaged items should be refrigerated if possible, and submitted to the laboratory as soon as possible.

1. Examples of large objects that can be cut, and that could have seminal stains on them, are carpeting, bedding, and upholstery.
2. Document the evidence as previously described.
3. Use a clean scalpel or scissors to cut the stained area from the rest of its surface.
4. Place each cutting in a separate piece of clean paper.
5. Make a druggist fold package to secure the evidence and avoid any contamination.
6. Place the druggist fold into an appropriate paper container, seal the container, and label properly.

1. Examples of these surfaces are floors, counters and metal surfaces.
2. Document the seminal stain evidence as previously described.
3. Use a clean scalpel to scrape the semen stain onto clean paper, and fold the paper into a druggist fold container.
4. Clean the scalpel in between each use to avoid any contamination.
5. Each druggist fold should be placed into its own appropriate paper container.
6. Each container should be sealed and labeled properly.

1. Sexual assault victims are always medically examined in hospitals.
2. Physical evidence should be collected using established procedures.
3. A standard rape kit should be used to collect vaginal, oral and anal evidence as necessary.
4. Each item of evidence should be packaged, sealed and labeled properly.
5. Evidence should be delivered to the laboratory as soon as possible.

3. Tissue, Organ and Bone Fresh Tissue, Organ or Bone

1. Each item of evidence should be described in notes, and documented by photography, sketches or videotaping.
2. This type of evidence item can be picked up with a clean pair of forceps.
3. Each item should be placed in a clean container without any added fixatives.
4. Each container should be properly sealed and labeled, and stored in a freezer.
5. Evidence should be submitted to the laboratory as soon as possible.

1. Each item of evidence should be photographed and sketched before collection. The size, shape, any pattern, and spatial relationships to the rest of the scene should be properly documented.
2. Each item can be picked up with a clean-gloved hand. Evidence still connected should be collected together.
3. Be careful not to contaminate any item with material from another item. Change gloves for every item.
4. Each item should be placed in a clean container, the container then sealed and properly labeled as previously described.
5. Evidence can be stored at room temperature, and submitted to the laboratory as soon as possible.

1. Liquid urine or saliva should be transferred to a clean, sterilized container (plastic or glass bottle) as soon as possible.
2. Each container should be sealed and labeled properly.
3. Evidence should be stored in a refrigerator, and submitted to the laboratory as soon as possible.

1. Urine stains, saliva stains and other body fluid stains can be collected as is, or removed from their substrata by scraping or cutting.
2. Place each stain sample in a clean, paper container. Scrapings or cuttings should be collected in a druggist fold made from clean paper. The druggist fold is then placed into a secondary paper container.
3. Containers should be sealed and labeled properly.
4. Samples should be transported to the laboratory as soon as possible.

5. Hair Evidence

1. Hair evidence can be picked up using a clean pair of forceps.
2. Each group of hair evidence items should be packaged separately, the package then sealed and labeled properly.
3. Exercise care in collection so as not to damage any hair root tissue present.
4. Hairs mixed with blood, tissue or other body fluids should be treated with care. Each item should be placed in a clean container that is then sealed and labeled properly.
5. Evidence should be stored in a refrigerator and submitted to the laboratory as soon as possible.

4. Laboratory Guidelines for Processing DNA Evidence

Once items have been collected and transported to the forensic science laboratory, the following are recommended as guidelines for processing each item of evidence submitted for DNA typing.

1. Physical evidence should be submitted to the laboratory with a transmittal letter, inventory sheet, and notation of the type of examination requested for each item.
2. All the evidence should be received according to standard laboratory procedure, and a unique case number should be assigned.
3. The case number, number and types of exhibits in the case, should be checked against the submission form. Any discrepancies should be noted and corrected.
4. Each package should be checked for packaging, sealing and labeling. Any sign of improper packaging, sealing or labeling should be noted.
5. Any sign of leakage or staining of packaging should also be noted.
6. Any important information regarding a DNA typing request and its relationship to case facts should be recorded on the submission form.
7. A receipt for evidence should be issued showing the date, time, submitting agency, submitter’s name, case number, item numbers, and the receiver’s name.
8. Physical evidence to be subjected to DNA analysis should be transmitted to the DNA unit as soon as possible and stored properly.

Once the DNA unit has received the case, and the case has been assigned to an examiner, the following are recommended as guidelines for the initial processing of evidence prior to DNA analysis.

1. An evidence examination form should be used to record the preliminary processing of each item. Information to be entered concerning the evidence includes:

1. Package description
2. Label information
3. Description of evidence
4. Any other item of evidence in the same package
5. Case number and item number
6. Date and name of examiner

2. Photography, notes and sketches should be used to document the location and pattern of the stained area if necessary.
3. The location, size and condition of any biological stain pattern should be recorded.
4. Any preliminary test results and any trace evidence recovered should be recorded.
5. Testing results on each item should be entered on the appropriate worksheet.
6. A form should be used to record information about each sample to be subjected to DNA analysis. Information that should be included is as follows:

1. Case number
2. Item description and number
3. Stain location
4. Size and pattern of stain
5. Mixed fluid stain condition
6. Amount of sample
7. Extraction tube number

7. Each sample for DNA testing should be removed from its environment with extreme care to avoid any misnumbering or contamination.
8. Every effort should be made to preserve a portion of the sample for possible future analysis. Such saved specimens should be stored in a freezer.
9. Each specimen for DNA analysis removed from its environment should be placed in a separate container, package or tube.
10. Each specimen for DNA analysis should be documented on an inventory sheet prior to the extraction step.
11. A blank control sample should be collected for items that are to be analyzed by PCR methods.
12. Unused portions of specimens should be recorded, repackaged, resealed, labeled, and stored in a freezer.