1. Collection of DNA, Blood, Saliva and Semen

3. Physical Evidence & Biological Evidence
Physical evidence is any tangible object that can connect an offender to a crime scene.
Biological evidence, which contains DNA, is a type of physical evidence. However, biological evidence is not always visible to the naked eye. DNA testing has expanded the types of useful biological evidence. All biological evidence found at crime scenes can be subjected to DNA testing. Samples such as feces and vomit can be tested, but may not be routinely accepted by laboratories for testing.

4. DNA Collection & Comparison
Overview:
Investigators gather samples from the crime scene and from suspects and then analyze it for a set of specific DNA regions or markers.
A match of one marker is not usually unique, but if a sample matches four or five markers, there is a very good chance it is a match.

5. DNA testing has expanded the types of useful biological evidence.
All biological evidence found at crime scenes can be subjected to DNA testing.
Samples such as feces and vomit can be tested, but may not be routinely accepted by laboratories for testing.

6. Sources of DNA at Crime Scenes
Examples of sources from real cases:
Saliva on the stamp of a stalker’s threatening letter
Skin cells shed on a ligature of a strangled victim
Perspiration on a baseball cap discarded by a rapist was compared with the DNA in the saliva swabbed from a bite mark on a different rape victim
DNA analysis of a single hair (without the root) found deep in a victim’s throat
Maggots can contain DNA
of a perpetrator

7. DNA evidence Evidence Possible Location of DNA on the Evidence
Source of DNA
baseball bat or similar weapon
handle, end
sweat, skin, blood, tissue
hat, bandanna, or mask
inside
sweat, hair, dandruff
eyeglasses
nose or ear pieces, lens
sweat, skin
facial tissue, cotton swab
surface area
mucus, blood, sweat, semen, ear wax
dirty laundry
blood, sweat, semen
toothpick
tips
saliva
used cigarette
cigarette butt
stamp or envelope
licked area
tape or ligature
inside/outside surface
skin, sweat
bottle, can, or glass
sides, mouthpiece
saliva, sweat
used condom
semen, vaginal or rectal cells
blanket, pillow, sheet
sweat, hair, semen, urine, saliva
"through and through" bullet
outside surface
blood, tissue
bite mark
person's skin or clothing
fingernail, partial fingernail
scrapings
blood, sweat, tissue

8. DNA Collection & Comparison
DNA is collected at crime scenes in a variety of ways using tools such as:
Smear slides, scalpels, tweezers, scissors, sterile cloth squares, UV light, luminol and/or blood collection kits (for sample collection of suspects or living victims)
DNA samples can be from:
Saliva, blood, hair strands, skin, finger or toe nails, and/or a tooth with root material

9. Blood Collection How is blood collected? Blood on Clothing?
Investigators submit whole pieces of clothing or they may use a sterile cloth square and a small amount of distilled water
Dried blood on furniture?
Investigators send the whole object to the lab
Dried blood on a wall, tub or some other object too big or difficult to move to the lab?
Investigators scrape the blood sample into a sterile container for further analysis

10. Crime Scene Integrity
Protection of the crime scene is essential to the protection of evidence.
Safeguarding and preserving evidence is fundamental to the successful solution of a crime.
Include descriptions of whether evidence was found wet or dry. An example of this documentation would include blood spatters.

11. Contamination
Refrain from smoking, eating, drinking, littering or any other actions which could compromise the crime scene.
Because DNA evidence is more sensitive than other types of evidence, law enforcement personnel should be especially aware of their actions at the scene to prevent inadvertent contamination of evidence.

12. In addition, if laboratory analysis reveals that DNA evidence was contaminated, it may be necessary to identify persons who have handled that evidence.
In processing the evidence, the fewer people handling the evidence, the better. There is less chance of contamination and a shorter chain of custody for court admissibility hearings.

13. Transportation of DNA Evidence
Maintain chain of custody and also be aware that direct sunlight and warmer conditions may degrade DNA.
Avoid storing evidence in places that may get hot, such as the trunk of the police car. To best preserve DNA evidence, store in a cold environment.

14. Any probative biological sample that has been stored dry or frozen, regardless of age, may be considered for DNA analysis.
Nuclear DNA from blood and semen stains more than 20 years old has been analyzed successfully using polymerase chain reaction (PCR)

15. Samples that have been stored wet for an extended period of time should be considered for testing only using PCR and may be unsuitable for DNA analysis.
Mitochondrial DNA analysis has been performed on very old bones, teeth, and hair samples.

16. Samples generally considered unsuitable for testing with current techniques include embalmed bodies (with the possible exception of bone or plucked hairs), pathology or fetal tissue samples that have been immersed in formaldehyde or formalin for more than a few hours (with the notable exception of pathology paraffin blocks and slides ), and urine stains.
Other samples such as feces, fecal stains, and vomit can potentially be tested, but are not routinely accepted by most laboratories for testing.

17. How can DNA evidence be planted??
Sneezing or coughing over evidence
Person touches their mouth, nose or other part of the face and then touches the area that may contain the DNA to be tested.
Scene personnel can deposit hairs, fibers, or trace material from their clothing
Wind can carry in contaminants

18. Blood Stains
Blood that is in liquid pools should be picked up on a gauze pad or other clean sterile cotton cloth and allowed to air dry thoroughly, at room temperature. It should be refrigerated or frozen as soon as possible and brought to the Laboratory as quickly as possible. Delays beyond 48 hours may make the samples useless.

19. Blood Stains
If close to the Laboratory, deliver stained object immediately keeping it cool but not frozen.
If unable to deliver to the Laboratory, or if the object must be mailed, allow the stain to air dry completely before packaging.
Do not heat stained material or place it in bright sunlight to dry. Hang clothing and similar articles in a room where there is adequate ventilation.
If not completely dry, label and roll in paper or place in a brown paper bag or box and seal and label container. Place only one item in each container. Do not use plastic containers.

20. Dried Blood Stains
On clothing, if possible, wrap the item in clean paper, place the article in a brown paper bag or box and seal and label container.
Do not attempt to remove stains from the cloth. 
On small solid objects, send the whole stained object to the Laboratory, after labeling and packaging.
On large solid objects, cover the stained area with clean paper and seal the edges down with tape to prevent loss or contamination. If impractical to deliver the whole object to the Laboratory, scrape the stain onto a clean piece of paper, which can be folded and placed in an envelope.
Do not scrape directly into evidence envelope. Scrape blood from objects using a freshly washed and dried knife or similar tool. Wash and dry the tool before each stain is scraped off. Seal and mark the envelope.
Do not mix dried stains. Place each stain in a separate envelope.
Never attempt to wipe dried stains from an object using a moistened cloth or paper.

21. https://prezi.com/pir8x4mu6rcf/how-is-blood-evidence-collected-and-packaged/

22. Saliva
Collect on a sterile gauze pad or swabs, allow to air dry and package in paper.
Do not use plastic containers.

23. Semen Stains
Seminal stains are often, but not always, found on clothing, blankets, sheets. Allow any stains to air dry, wrap in paper, and package evidence in paper bags. Do not use plastic bags.
For sex offense cases, the victim should always be examined by a physician. A Sexual Assault Evidence Collection Kit is used to collect evidence from the victim. It is very important that the instructions on the kit be followed with care in order to gain the greatest benefit from the collected evidence.
Label all garments such as undershorts, panties, or other exhibits and package each garment separately.
If damp, allow fabric to dry completely before packaging.
Handle fabrics as little as possible.

24. Chain of Custody
The chain of custody of evidence is a record of individuals who have had physical possession of the evidence.
Documentation is critical to maintaining the integrity of the chain of custody.
Maintaining the chain of custody is vital for any type of evidence. In addition, if laboratory analysis reveals that DNA evidence was contaminated, it may be necessary to identify persons who have handled that evidence.
In processing the evidence, the fewer people handling the evidence, the better. There is less chance of contamination and a shorter chain of custody for court admissibility hearings.