Footwear and Tire Tracks

Tires and shoes have one thing in common – they both leave patterns when they are used. A tire can leave a pattern in the dirt next to a house, or a shoe can leave a transfer of blood when a criminal leaves a crime scene. The patterns left by tires and shoes are often unique and can be examined to help investigators narrow the field of suspects.

Investigators look at 3 main characteristics when examining a pattern or imprint left by a shoe or tire: class, wear, and individual characteristics.

-Class characteristics: These are results from manufacturing. General class characteristics include the make and model of a tire, and limited involved the specific mold used to make a certain tire.

-Wear characteristics: As a shoe or tire is used more, more of it will change depending on how long it has been used. A tire 500 miles old will be very different from a tire that is 45,000 miles old. Shoes will wear differently based on how the owner walks and how long the shoes have been used.

-Individual characteristics: These are characteristics that are not a result of the manufacturing process. For example, if I stepped on a nail and it went through the bottom of my shoe, the mark left by the nail would be considered an individual characteristic.

According to Forensic Science Simplified, an accurate examination of a shoe or tire can give investigators clues such as “where the crime occurred, the number of parties or vehicles present, the direction a person may have traveled before, during, or after the crime, whether a person was on foot, and other crime scenes connected to a perpetrator.”

Prints are divided into 3 categories: visible (such as a blood shoe print), latent (not visible to the naked eye, such as a print on a sidewalk), and plastic (such a shoe print in the mud). Casting is often used to collect plastic prints, like a shoe print left in the mud. Lifting techniques can also be used – and there are several of those that can be used as well. These techniques include adhesive (adhesive is placed over a print commonly dusted with fingerprint powder then lifted off), gelatin (less sticky than an adhesive lifter, so it can be used without tearing fragile materials that a print may be on), and electrostatic lifting (particles are electrically charged and can then be attached to lifting film).

In this picture, investigators are inking a tire and driving over paper so that prints can be compared.

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Investigators carefully examine any evidence they receive for clues to where it came from and who could have owned or wore the item that made a certain print. There are databases full of prints from tires and shoes that can be used to make comparisons. It is important that the examination is made precisely and carefully, or a valuable clue could be missed and a perpetrator could get away with a crime.

Source: “Footwear and Tire Track Examination.” Forensic Science Simplified. 2013. Web. 9 Apr. 2016.

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Ballistics

The impact of a good firearms investigator is invaluable to an investigation where a firearm is involved, especially in the case of murder. The ultimate goal of ballistics is to determine if the bullet or casing in question came from a particular firearm.

There can be any amount of evidence in a case that needs to be tested. It could be anything from one bullet fragment to hundreds of casings and ammunition that came from several different firearms. In both cases, the testing done is equally important. The smallest sample can still provide clues to what actually happened.

There are two types of gunshot residue that can be looked at: the type taken from the suspect’s hands, and the type that is collected off the suspect’s clothing. The first type is used to determine if the suspect actually handled or fired the gun or not. If he did not, there will be no residue, and if he did, there will be residue left. The second type is used to determine muzzle-to-target distance, which would tell investigators how far away from the target the shooter was when the trigger was pulled.

Ballistics analysis is performed by trained professionals in labs all over the country. These professionals will look at anything from fired bullets to casings. A microscope is used so no small details are missed or mistaken. Most labs will have a method they use to discharge a weapon, then collect the fired bullet and casings. Usually this is done in  a tank of water, but sometimes a box containing cotton waste is used. Investigators can also look at the marks on a bullet collected as evidence and compare them to the grooves inside of a barrel it is suspected the bullet was fired from and determine they match or do not.

comparison pic

In this picture, two cartridge cases are being compared. One was recovered from a crime scene and the other was fired from the weapon in the lab. Note how the marks line up and are similar on both casings.

A proper and thorough examination of bullets, casings, bullet fragments, grooves in the barrel of a gun, or any other number of aspects of ballistics is extremely important to a case under investigation. The results of an examination can prove guilt or innocence, and have the power to change lives and bring closure.

Source: “A Simplified Guide to Firearms Examination.” Forensic Science Simplified. 2013. Web. 25 March 2016.

Questioned Documents

There can be many questions about the authenticity of a document, who a sample of handwriting may belong to, or the validity of a suicide note. In all these examples, there exists specialists that are trained to examine every aspect of a document and determine if it is authentic or not. These examiners use several techniques to analyze any evidence in their possession.

  • Indented impressions – basically, this is the idea that if someone wrote a note on a pad of paper and ripped the top sheet off, the sheets underneath could be examined to look at the marks that pressed through the first sheet and onto the ones below.
  • Alterations, obliterations, erasures, and page substitutions – different types of light, such as infrared or ultraviolet,  react differently to types of inks. This can show what has been added or removed from the document in question.
  • Individual dye components – a small sample from a document can be cut and tested. It can then be matched to an ink library run by the Secret Service, which has collected all ink types produced since 1920.
  • Machine-written documents – different machines print in different ways, and can also use unique inks. Both of these factors can be looked at the determine the type of printer a document came from.
  • Seals and Stamps – marks made such as “rubber stamp impressions, embossed seals, watermarks, or other mechanically printed marks” can all be examined for any unique features or clues to where the document came from (“A Simplified Guide”).
  • Handwriting Analyzation – with a large enough sample of handwriting from two different people, a comparison can be made. No one writes the same way one hundred percent of the time, so even if someone writes very neatly, a skilled investigator will be able to pick up on differences in the writing, such as hesitation or a mistake that was covered up. The age of the person who wrote the document being examined must also be taken into account, as a sample taken from an eight year old will not look the same as a sample given from that same person a few years later at twelve years old, because their writing style develops as they age.

The results from an examination of documents can sometimes be enough to convict suspects of anything from changing the amount on a check to murder. It is very difficult to fake or change a document and get away with it without suspicion.

Source: “A Simplified Guide to Forensic Document Examination.” Forensic Science Simplified. 2013. Web. 19 March 2016.

Arson

Arson is a destructive crime in today’s world, with the capability of destroying valuable property and causing thousands of dollars in damage. There are three types of fire starters – pyromaniacs, arsonists, and juvenile fire starters. Pyromaniacs get some sort of gratification from starting fires and very methodical about it. Arsonists set fires for specific reasons such as profit, revenge, or attention. Juvenile fire starters are under 21 years of age. They usually start fires in their homes, schools, or vacant buildings. Because they are younger, they are often gullible and can be coerced into setting fires for less than a professional arsonist can be hired for.

In any fire, there will be a point of origin, or the place the fire started or was set. The point of origin can be found by locating the spot with the greatest amount of damage. It makes sense that the point of origin will be the most damaged and the extent of damage will lessen the farther away from the point of origin it is located. Even if a structure is completely burned to the ground, a skilled investigator will still be able to locate the point of origin.

Signs of arson:

  • Irregular burn patterns: these indicate that an accelerant was used in the fire. Gasoline and lacquer thinner are examples of accelerants, which are commonly poured on a surface such as the floor and set on fire so the fire will be bigger and spread faster. The picture below is an example of a situation where an accelerant was used on a tile floor.

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  • A quickly burning fire: pine wood burns at a rate of ¾ an inch per hour. A quickly burning fire can indicate that an accelerant was used.
  • A claim of an electrical fire: less than 7% of fires are actually results from an electrical fire. Wires should be closely investigated to either back up or disprove the claim.
  • Inventory or possession shortage: often if a homeowner or business owner is planning to burn their property and claim insurance, they will remove the most valuable items. Inventory may be unusually low or the homeowner may have recently removed valuable items from the home.
  • Total destruction of a car: often if the fire begins in the engine block of a vehicle, it will not spread into the passenger compartment on its own. Other signs of arson in a vehicle include cut fuel lines, missing gas caps, or used matches. The springs from the seats of the car can also clue in investigators that the fire was a product of arson. The heat from a car fire alone will not be hot enough to cave in the roof of a car or cause seat springs to sag or become distended. Both of these situations are clues that an accelerant was used in a vehicle fire and was therefore arson. Distended seat springs can be seen below.

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In a case of suspected arson, investigators look for three things to convict a suspect – an intentionally set fire, motive, and opportunity, also called the “arson triangle.” Let’s say Bob’s warehouse burns down one night, but it was old and falling apart anyway and in need of repairs tht Bob can’t afford at the moment. Investigators found clues that an accelerant was used – there’s your intentionally set fire. Bob is trying to collect insurance on his warehouse and whatever was in it – there’s the motive. But Bob was out at a bar the night his warehouse burned to the ground – he has an alibi so he had no opportunity to set the fire. This doesn’t mean investigators won’t dig deeper to try to find out who set the fire (maybe Bob hired someone to torch his warehouse), but for now, Bob is in the clear as far as an arson suspect goes.

Arson investigation can be very involved and can take a while, but it is important that it be processed correctly and accurately. If it is not, an arsonist may get away with setting fires and destroying property.

Source: Barracato, John S. Fire…Is It Arson? U.S.A.: Aetna, 1979. Print.

Identifying a Body without DNA

In this day and age with advanced technology, DNA testing is widely used to identify human remains even when the body is partially dissolved, cut up, or burned. Sometimes, however, it is better to use other methods of identification because DNA testing can be expensive and in the case of remains not preserved well, not effective.

There are 3 alternate ways to identify a body:

  1. Dental x-rays and Dentures

Unique dental aspects, like “tooth root curvature, tooth position, impacted teeth, extra teeth, and tooth crown anomalies” often are preserved even if other parts of the body do not (“3 Ways to Identify”). Any x-rays taken before the decedent died can be compared to any taken after the person died. Dentures work almost the same way. They are uniquely shaped and formed for each person who uses them, and some today are inscribed with the name or initials of the person they belong to, which makes identifying the owner even easier.

dental_xrays

2. Surgical Implants

Because surgical implants are constructed of highly durable materials, and often placed deep in the body, they usually survive the conditions that cause the rest of the body to deteriorate. They also are usually marked with serial numbers that can be traced back to the specific patient they belong to. Examples of these surgical implants include hip and knee prosthetics, pacemakers, or coronary artery stents (“3 Ways to Identify”).

3. Skeletal diseases or injuries

Certain diseases can cause enough damage to the skeletal system that it can be used to identify a body if only bones are found. Diseases such as tuberculosis, syphilis, or psoriasis can do so much damage that it is visible in an x-ray (“3 Ways to Identify”). Fractures or already healed breaks in bones can also be clues to the identity of a person. Any unique fractures can be compared to recent medical records and compared to the decedent for matches.

Even though DNA is often the more convenient route to go, it is not always possible if the body is in poor condition. These methods are commonly used when other techniques are not possible, and can be highly accurate if the tests are performed correctly.

Source: “3 Ways to Identify a Body When DNA is Not An Option.” Forensic Outreach. N.d. Web. 6 Mar. 2016.

 

 

 

Detection Dogs

Because dogs have a much better sense of smell than humans, they are often trained and used to detect scents that humans can’t pick up on. There are a few different types of detection dogs, and the differences are important when considering what dog to use for a specific task. The handler, or person training and working with the dog, also needs to be able to read the dog well and pick up on if the dog is detecting something or not.

Types of detection dogs:

  1. Narcotics dogs – they are trained to pick up the scent of drugs and are commonly used at airports. With enough training, they will be able to pick up on the scent of drugs even when it is being masked with another scent.
  2. Tracking dogs – these dogs are trained to sniff a scent and follow only that scent. For instance, if a suspect of a crime is on the run, the handler can have the dog smell something belonging to the suspect such as a pillowcase or a piece of clothing. The dog will then follow that specific scent wherever it is present and can lead investigators to the suspect.
  3. Bomb detection dogs – these dogs are trained to sniff out any substance of a bomb if it is present. It is trained to not disturb a scene, as an explosive could detonate, but will alert its handler to the presence of a bomb.
  4. Arson detection dogs – a dog trained to detect arson will sniff out the presence of accelerants commonly used by arsonists. Especially in a case where the damage of the fire covers a large area, these dogs are extremely valuable to show investigators where accelerants were used.
  5. Search and rescue dogs – when someone goes missing or is lost, these dogs are used. They are trained to be useful in a variety of environments, such as in snow or in heavy water.
  6. Body detector dogs – sometimes in situations like a landslide or earthquake, people may be trapped in the aftermath but are still alive. It is in situations like this that body detector dogs are brought in to find living humans so they can be rescued.
  7. Cadaver dogs – these dogs are trained to respond to decomposition, so when the presence of a decedent is suspected, these dogs are brought on scene to lead investigators to the body.
  8. Human remains specialist dogs – these dogs begin as cadaver dogs in general, sniffing out the presence of any decomposition. They are then further trained to respond only to a specific type of human remains.

The importance of these dogs is often not realized by the general public. I did not realize how important they were either, until I started at the coroner’s. They have a cadaver dog, Ino, that stays at the office and is used to detect decomposition. Recently Ino hit on a body of water where someone told investigators that someone committed suicide. Investigators have been diving there the past few days trying to recover a body. The work of detection dogs can be invaluable in their line of work, so it is essential that they be trained correctly to do their specific job.

Source: “Forensic Detection Dogs.” Kryptiks Lair German Dogs. N.D. Web. 27 February 2016.

Determining the Time of Death

The time of death is as simple as it sounds – it is the time at which someone dies. Time of death is categorized into 3 different types:

  • Physiological time of death: this is the time at which the person’s organs stop functioning and shut down.
  • Estimated time of death: this is an educated guess on time of death based on any information available to investigators.
  • Legal time of death: this is “time at which the body was discovered or physically pronounced dead by another individual” (“Estimating”).  Legal time of death is the time that is entered on a death certificate.

One method of determining time of death is to take the temperature of the decedent. Investigators use a math equation to help decide how long the person has been dead. Temperature can be taken using a rectal thermometer or by measuring the temperature of the liver, which provides a more accurate core temperature. When taking temperature, the location the body was found in must be taken into account as well. If a body was found in the middle of winter in a lake, that will affect the temperature reading.

Rigor mortis can also help investigators determine the time of death. Rigor mortis is the “natural contracting and relaxation of the body’s muscles caused by changes in the body’s chemical balances” (“Estimating”). Rigor begins in the smaller muscles and works its way through the body. It begins soon after death and can last up to 30 hours after the person has died. It will leave the body eventually, so if a body is found and rigor is not present, it can be concluded that the decedent passed more than 30 hours previously.

For example, there was a man I took the fingerprints of my first week at my internship. Normally the elbow is bent so fingerprints are easier to take, but the man was still in rigor. Time of death had already been determined because there were witnesses to his death, but if it had been unknown, the rigor present in his body could have been a clue.

The insects found at a scene (as gross as it sounds) can also be used to estimate death. The insects present and how far along they are in their life cycle can provide insight to investigators.

When time of death is not known, investigators have a variety of ways to help them estimate the time of death. This can be valuable especially to death investigations when time of death can narrow down a suspect list.

Source: Claridge, Jack. “Estimating The Time of Death.” Explore Forensics. 21 Feb. 2016. Web. 19 Feb. 2016.