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)

Interactive Game

http://www.museevirtuel-virtualmuseum.ca/sgc-cms/expositions-exhibitions/detective-investigator/en/game/index.php

This was an interesting little game. I thought I would complete this to break up my posts. I must admit, at times I felt a little like Scooby Doo and the gang were with me and we were going to find out who the monster behind the mask was. The game was a bit cheesy and I had to go to the help section to see that there were actually four separate clues to each scene. The grandfather clock for time of death? Not something I would have considered looking at when observing. This is a good little game for someone who may not have the knowledge that an upper level student has. I did win the game and "Pat the Rat" swam down the river.

Crime Scene Photography

There are basic guidelines when photographing a crime scene. In investigator should expect to:

• Photograph the scene in an unaltered condition.
• Fill the camera frame with the object being photographed.
• Avoid shadows 
• Maximize depth of field
• Always keep a log

  A crime scene should be photographed just as it is when the investigator arrives on the scene. The only exception to this rule is when medical care is provided to a victim (s). Photos should be taken in order first with outside areas of the scene, adjacent areas where activity may have taken place prior to or after the crime then moving on to photos that are of the scene itself. The first photo that should be taken is of the photography log form. This should include the type of scene, the case number, location and a description of the camera being used at the scene. This should be SOP at all scenes to provide a uniform way of operation. This SOP would also be useful to denote when the scene begins and ends, especially if an investigator has multiple scenes in one day or the beginning and ending of scenes on one roll of film. To begin:

• Outer areas of the scene are photographed such as probably entry and exit, rooms that are next to the scene and the wall areas of the immediate scene. Photos need to be taken from different angles or points of view. For example a 6' investigator should take photos from less than 6' in the air and at the eye levels of any witnesses present. If there is a deceased victim at the scene all measures should be taken to photograph the area before the victim is moved in any way. Different points of view should be taken in order to show the victim in relation to the scene itself. If a victim is leaned against a wall, photos should be taken of all sides as well as facing the victim. When taking these photos it is common practice to choose one object at the scene and include it in all photos so that a point of reference can be established. If there are witnesses then photos should be taken of them standing where they were when they witnessed said crime.
• The next set of photographs should include evidence found at the scene. For example, if an investigator found shell casings at the scene of a shooting, evidence markers would be placed where the shell casings were located. The investigator would then take photos at about half to a third of the distance of the first set of photos. If there was a table or dresser in the scene area, an overview photo should be taken to identify the items on the table. The center or area where the victim was found should be photographed in great detail from many angles to provide relationship to the area.
• Close up photos should then be taken. These should include 90-degree angle photos of any visible evidence. These photos should be taken first without and then with evidence markers. To use our shooting scene for another example, an investigator would first photograph the shell casing, then the casing with an evidence marker and then finally with a ruler or some type of measurement too to show the scale and size of the casings.

There are several types of lenses that can be used to take the above photos. If an investigator needs to photograph an object at a great distance, perhaps the view from a window, a telephoto lens could be used. A wide angle lens could also be used in this case. When taking close up photos, an investigator could use a macro lens which is designed to take photos from a distance of less than 50 mm and a 1:2 magnification. This is especially useful in photos of tool marks or visible fibers as well. If using a multipurpose camera, an investigator can also adjust shutter speeds to account for the light level available.
Not every case will be in a brightly lit room with a deceased victim. There are other situations that call for a different technique:

• Night scenes- If possible, wait until morning. If not, setting up floodlights is an option but photos should be taken again in the daylight as scenes look completely different. If there are no floodlights and one cannot wait until morning there is a technique called "painting with light". Place the camera on a tripod and  lock the shutter of the camera open. Use the flash of the camera three or four times and then close the shutter. This will provide an investigator with a lit photograph in total darkness.
• Indoor scenes- Starting at the outer areas of the scene and working towards the center, photograph all areas including entry and exit. Then, in order of clockwise take photos from each corner and the middle points of the corners then move on to medium and close range photos.
• Outdoor scenes- If this is a vehicle accident, collect photos of any traffic signs near the area then move on to the clockwise overview photos at the outer areas of the scene. Remember to use GPS coordinates and track them on the log. Most cameras are made using a GPS but a smartphone app will also give coordinates. When photographing the vehicle, it is practice to first photograph the front then left, back then right. Make sure and photograph the license plate and the vin number of the vehicle if possible. If it is a traffic accident, show the weather conditions and even the traffic pattern, catch tire marks. Take several photos from the point of view of each vehicles approach or a person's walk route. Note the condition of each vehicle, inside and out paying attention to airbags, position of drivers seat, and pedals of vehicle.
• Arson- This is another example of taking overview shots of the area. Photograph where the scene is located, people observing the area,  and overview of the burned area. In this case, capture whatever may be a point of origin of the fire.
• Sexual assault- Great care and concern should be taken of the victim. Capture the area where the assault happened. Take medium as well as close up photos of any injuries including bite marks. Photograph the clothing, if any that the victim was wearing.
• Impression Photography- Close up, 90 degree photos of footwear or tire impressions need to be taken before any casts are made. Photos of the direction the impressions came from are also important to note. Be sure and use a scale in the photos.
• Bloodstain photography- taking overview and closer range photos of blood stains help to show their location as well as the direction gravity is pulling the blood, this will help determine the crime as well as the position the victim was in when the bloodstain happened. Photographing a bloodstain requires a scale as well.
• Latent fingerprints- A fingerprint camera is used so that the print will show all detail. If this camera is not available, black and white photos will help to enhance the detail. Include a label in the photo so the place it was taken can be noted.

• Shootings- When photographing a shooting scene, take overview photos before tagging or photographing evidence.  Photos from the point of view of any witnesses as well as the points of view of those involved in the shooting should be taken. If/when a bullet is found, capture the area of the impact as well as the bullet itself. 

Reference: Forensic Science. Richard Saferstein. 2013

Famous cases and forensics

On August 15, 1982 while floating downriver on a raft, a man saw what he thought was a mannequin floating in the water. After falling in the river trying to move what turned out to be a dead body, the man saw at least one other partially clothed woman in the river. He called for help and soon the police came. The officer didn’t believe the man and waded into the river and made his own discovery. This was three in the string of several female victims found in or near the river over the past several months. It had been determined that all of them had died from strangulation. The Green River Killer was born.

            A special team was assembled to work on the cases and they were inundated with information. The officers were so overwhelmed a fair amount of their information became misplaced. Due to all the information the police asked for volunteers to help. What they were able to find out was that most of the women were prostitutes in Seattle. Interviews of many of the women failed to produce anything but one woman did give them a report of a man who had raped her and also talked about the Green River killings, that man drive a blue and white truck. Other accounts of the same truck poured in and Charles Clinton Clark was arrested. Clark admitted he assaulted some of the women but he released his victims after he attacked them and he had an alibi for the times of the Green River killings.

            It was after a FBI profile of the murderer came out that the police started to suspect someone that had volunteered to help them, a taxi driver named.  During the investigation, at least thirty more girls were found dead along the river or connected in some way to the same killer. Gary Ridgeway was questioned multiple times in 1987, a search warrant was served on his home and “bodily samples” were taken from Ridgeway as part of the search warrant. The task force did not know it at the time but they were making it possible to discover a serial killer, albeit many years down the road. Hair and saliva samples were taken from Ridgeway but he passed a polygraph test and was released. The case went cold for many years until the science of DNA came along and Ridgeway was arrested on November 30, 2001. Ridgeway had left a trademark in his victims. He would enter them from behind while strangling them, he ejaculated inside them and then pushed rocks into their vagina. Ridgeway was preserving his own evidence and after DNA testing of three of his victims it came back as a match to the hair and saliva samples taken from him twenty years prior.

            Very simply put, every cell in the body contains about one foot of DNA packed into less than a millimeter of space. This DNA contains all the information about a person, their hair color, eye color, matches up to a person’s relatives and tells us virtually everything we would want to know about someone. When Ridgeway ejaculated into his victims and then pushed rocks into their vagina he preserved his DNA and investigators were able to obtain samples as evidence even though they did not know at the time that the science of DNA would catch their killer. Those samples were compared to the DNA Ridgeway left in his victims and were found to be a match.