I went to the CSI webpage and tried to complete the burning rain. I was not able to finish for some reason but while I was there I was interested to learn that that there are over 4 million DNA samples to match in CODIS. I was also interested to learn about facial reconstruction and the process that one goes through to reconstruct a face from a skeleton. I had seen it on TV but of course they don't really get into the entire process. I was also able to find out that the process for going through a suspect or victim's computer is actually done by making a copy of the hard drive instead of actually going through the computer itself. I apologize for not being able to completely finish.

Blood typing...Blood stains and DNA

In the simplest of explanations, blood is made up of cells (red and white blood cells and platelets), enzymes, proteins, water, inorganic substances. The majority of human blood is water (over 50%). Red blood cells transport oxygen throughout the body and white blood cells fight foreign bodies such as bacteria and viruses in the body. Antigens on red blood cells help to make up how we classify blood such as types A, B, or O. If a person has type B blood then they are classified as having type B antigens on their red blood cells. Mixing certain antigens with others will cause the blood to clot and the recipient of the blood to most likely die. Certain blood types can go together such as O+. For example, when type A blood is examined, antigen B or anti B will be found but there will not be any anti A found. Initial testing of blood at a crime scene may show evidence of type B blood. If the victim is type O and the suspect is type A, we can rule out our initial suspect because he or she does not have the blood type matching blood found at the scene and move on to another suspect.

When an investigator finds what he or she believes to be a bloodstain two questions must be answered right away. First of all, is the stain in fact blood and if it is, is it human blood or did it come from some kind of animal? If it is human blood, what type is it and is it that same type as the victim or could it be someone else’s blood. To answer the first question, a color test can be done rather quickly and right in the field. The Kastle-Meyer Color test is based on the idea that blood will turn a certain color when chemicals are added to it. Swabbing a suspected blood stain and adding the reagent phenolphthalein and hydrogen peroxide to the swab, blood will turn a bright pink color. There are cases where certain vegetables will also produce this color but having suspect vegetable stains at a crime scene is a remote possibility.

As we have all seen on television, the chemical luminol makes a blood stain glow in a darkened room; this is especially useful when testing large areas such as an entire bathroom or even walls and floors in a large living room. When darkening a room is not an option, a chemical called Bluestar will also make blood glow under normal conditions. These are very sensitive tests and blood that has seemingly been washed away or cleaned will still show when these chemicals are added. An advantage to these chemicals is when a blood stain is found when using luminol or Bluestar, DNA is not effected.

Now that we have determined that the suspected stain is in fact blood, we must now determine if it is human blood or if it came from an animal. By adding human blood to rabbit blood and then extracting the mix and separating the antibodies created, a human antiserum or precipitin test is created. To explain, by layering the suspect blood on top of the human antiserum in a test tube, human blood will cause a ring or band to form between the suspect or now human blood and the serum. Another way to test a suspect bloodstain is to place antiserum and the suspect blood onto a special gel medium. If the blood is human blood, a line will form between the two compounds where the antigens and antibodies have been attracted to one another. This is an extremely sensitive test that can confirm human blood that has been tried for more than fifteen years or a tissue sample several thousand years old. Now that we A) know the stain is blood and B) know it is human blood, laboratory tests can be done to map the DNA in the blood cells to determine who the blood belongs to.

Safertein, Richard. Forensic Science, From the Crime Scene to the Crime Lab. 2013

Paint, glass and soil sample collection

Document the methods for collecting and preserving samples of paint, glass, and soil. What is the responsibility of the field examiner? What can the criminalist show in comparison, and what is needed for comparison?

The proper collection of evidence can literally make or break a case. OJ might be living out two life terms right now if evidence had been properly collected, documented, and of course brought to the station or lab instead of sitting in a detective’s car overnight. There are ways of collecting certain pieces of evidence and one must be careful to do the job correctly or the evidence you spent so long collecting could turn out to be unusable. The following will note the proper collection for:

Paint: Paint evidence is most often found at hit-and-run scenes. This may be in the form of transfer or paint chips. When paint chips are discovered at a scene they must be carefully collected in order to keep the chip intact. If tweezers are not available, a clean piece of paper may be used. If using paper, ensure that a druggist fold is used to maintain integrity. Be sure to properly document the papers. If using tweezers, a plastic container or vial is perfect. 

If the paint evidence is transfer, do not attempt to remove the paint from clothing or a bicycle. Package the items to the best of your ability and bring the entire thing for testing. When you have a suspect vehicle, collect your sample from an undamaged part of the car that is close to the area that struck. Collecting a sample from another part of the car all together might not result in a match because another area may have faded or even been replaced and repainted at some point in the car’s life.

When collecting a sample, a new disposable scalpel must be used each time and one should get a quarter-inch sample that goes all the way down to the bare metal, package each sample individually and note where on the vehicle it was taken from.

Glass: A careful examination of both your suspect and the crime scene is essential to finding and documenting glass evidence.  How many times have we broken a glass on the kitchen floor and thought we found every piece until we step on the one piece we missed because we didn’t see it? That one painful piece could have won us the case. There are several different types of glass and just as many scenarios where it should be collected. Broken pieces of a cars headlight at a hit-and-run, window glass found on a suspect, or painted or colored glass that might have been used as a weapon. If possible, collect at least one quarter inch of glass from the source, even if you don’t have a suspect now, you might find one down the road and there is still a chance that a match could be made. When collecting from the source, notate if the collection is interior or exterior glass such as the case in a double pane window. If it is not possible to know if the sample is interior or exterior an examination of the glass should show a certain amount of dirt, pain or even pollen on one side of the glass.  Be sure to package glass fragments in a solid container so that it does not break any further. Should you have a suspect, that person’s clothing and shoes should all be wrapped individually in paper wrappers and transported to the lab.

Soil: When a civilian thinks of soil they think of dirt. When an investigator thinks of soil, they consider rocks, leaves, animal scat, ashes, rocks and vegetation to be included in the collection of the dirt. The collection of any or all of these material is valuable as it shows it to be present in a particular location and differentiates it from other locations. Evidence such as this that is found on a suspects shoes or clothing may be able to prove that they were in said location instead of at their aunt’s mother’s best friend’s house or anywhere except admitting to being at the scene. When collection soil samples from a crime scene the first samples of course should be at the active site. Other samples must be taken however at set intervals within a 100- yard area to better prove the suspect was present in the immediate area. For example, if a victim was found beside a road and proper soil collection was done then we as investigators would think to pick up a half-stepped on piece of dog poop. A week from now, we may conduct a search on a suspect’s home and find a pair of boots with the other half of the dog poop on them. Having the original sample may enable a criminalist to place the suspect in the location of the scene.

When collecting a sample in most cases it is not necessary to dig down into the soil and a couple of tablespoons is a sufficient sample size to be tested. Place the soil in a plastic container and properly mark the container. If soil is found on a known suspect, the clothing and shoes must be collected into paper bags and marked for evidence. If collecting dirt from a suspect or victim’s vehicle, collect samples from inside the wheel wells of the vehicle as layers tend to build up in that area. Under the fenders and frames of the vehicle is another place to collect dirt evidence when searching a vehicle.

Tool marks and impressions

When arriving at the scene of a crime where it has been deemed that someone broke into a building it is important to make a clear record of those marks. A record will help to identify what kind of tool was used and, if a suspect is found a similar tool could be found in their possession when a lawful search is conducted. Whenever possible, the evidence in question should be brought to the lab for investigation. If that is not possible, several photos to scale should be taken of the area. After photographing the area, a silicone cast should be taken of all tool marks. The reason for using silicone instead of any other product is because of the clarity it gives the cast.

            After the item or the cast is taken to the lab for testing we can determine the tool that made the impressions. For example, if the tool marks showed class characteristics of a screwdriver then the investigative team will know to look for screwdrivers when conducting a search of a suspects belongings. If said screwdriver is found then it can be examined and compared to the tool marks in the cast. All tools have their own individual characteristic marks and if they have a high probability of matching we can determine that the subject likely used that tool to break into the building. Any crime scene investigator should know that if it appears they may have found the tool that was used they should NEVER press that tool into the area in question. If that tool is pressed into the area then the area will take on the characteristics of the tool when they may not have been there previously. One should never assume that just because there is a gun next to a gunshot victim that the gun is the same one that killed the victim. This is practicing objectivity when examining a crime scene.

            There are other types of impressions that can be found at a scene. For example, there may have been a break-in at the scene but a perpetrator had to have arrived on the scene in a vehicle or by foot. Either way, it is very important to photograph the impressions, to scale, from several angles and with the best contrast. After photographing, cast impressions should be taken of the tire or shoe impressions.  According to our textbook, the following is the recommended procedure for casting impressions:

1.      “Retrieve any fragments of debris that is not imbedded within the impression. Photograph the impression before and after retrieving debris; include a ruler in the photograph. A frame for containing the dental stone may be installed around an impression that is shallow or on an inclined surface.

2.      To solidify the soil, a fixative such as hair spray is used by holding the can about eighteen inches from the soil within the impression. Very lightly spray an even layer to the impression using a sweeping motion and taking care to avoid any damage to the impression.

3.      Wait ten minutes for the hairspray to dry.

4.      Add an appropriate amount of water to a premeasured amount of dental stone, usually ten to twelve fluid ounces of water to about 1.5 to 2 pounds of dental stone in a zip-lock bag.

5.      Pour the dental stone through an opening in the bag onto the ground beside the impression and allow it to run into the impression. Carefully disperse the stone into the impression so that it does not destroy the fine details of the impression. Continue pouring until the dental stone completely fills the impression to .5 to 1 inch in thickness. Label the wet plaster surface with the date, initials and any other required information for evidence.

6.      ‘When the cast no longer adheres to the soul and is relatively dry, remove the cast.”

(Saferstien, Richard. Forensic Science, From the Crime Scene to the Crime Lab. 2013 Pg 222)

If the impressions need to be shipped one should wait one to two days to make sure the impression is completely dry. When casting and packing these impressions it is very important to follow SOP and chain of custody.

      Tire and shoe markings are stored in a general file and is updated periodically by the manufactures. These types of markings such as the sole of a shoe are called class characteristics and can help narrow down a list of suspects but in no way does it absolutely exclude other suspects. Now, if the sole of that shoe had hash marks in it because the wearer was bored and carved on their shoe and the impressions also showed these hash marks then these would be considered individual characteristics and police would be free to pursue this suspect as their perpetrator. If it was determined that the victim was also bitten in the assault, several photos should be taken to document the bite so the court can issue a demand for a dental impression and it can be compared to the bite mark photographs for a match. Careful evidence collection is an important key to prosecuting a crime. The more careful the collection the better chance investigators have of solving the crime.

(Saferstien, Richard. Forensic Science, From the Crime Scene to the Crime Lab. 2013)