- SCIENCE IN CRIME - Fun Facts | BoysJoys


Science And Crime Detection

Modern detectives use a wide range of scientific techniques to help them identify and catch criminals

  • Fingerprinting
  • Fingerprinting is one of the oldest, most established forms of proving a suspect was present at a crime scene. Computers have enhanced the techniques used.

    Every person in the world has a unique set of ridges on their fingers. These are formed in the third and fourth month of pregnancy and remain unchanged for life - apart from size. In his book, Invisible Evidence, Bill O’Brien discusses the characteristics of fingerprints and how these are exposed at a crime scene.

    The Characteristics of Fingerprints

    Fingerprints are friction ridges that enable people to grasp things. They appear in three basic patterns:

    basic patterns

    There are no sebaceous glands in the skin of the hand but there is a greater concentration of sweat glands than in other parts of the body. When a person sweats, the mixture is 99 percent water and one percent fats and acids. The more a person sweats, the better the fingerprints left behind. Once the water has evaporated, the fats and acids remain in the form of a fingerprint.

    How Fingerprints are Revealed at a Crime Scene

    For over 100 years, fingerprints have been exposed by carefully brushing a fine powder across the area. Black powder is used on light-colored surfaces and white powder is used on dark surfaces. The print is then lifted with tape and placed on a clear acetate sheet.

    In a laboratory setting, a fuming tank may be used to expose fingerprints on non-absorbent and semi-absorbent items such as bottles, cans, plastic, glossy cardboard and tinfoil. It works by heating commercial-grade superglue to 100°C. These fumes are circulated through the tank and stick to the fingerprint, so setting it and making it firm. It is then treated with dyes to make it clearly visible.

    Absorbent surfaces such as wood, paper and plain cardboard tend to suck in fingerprints meaning a different technique must be used to expose them. Latent print examiners use ninhydrin, a chemical that helps detect amino acids that are found in sweat. After being mixed with a solvent, ninhydrin is applied to the surface in question and the result is bright purple fingerprints.

    Other chemicals and powders are used to reveal fingerprints on sticky surfaces such as adhesive tape and on thermal paper such as is used for till receipts and ATM slips.

  • DNA Testing
  • Everyone, except identical twins, has a one-of-a-kind DNA genome. The DNA molecule, a nucleic acid, is made of monomers called nucleotides, and the specific order in which nucleotides occur in a DNA molecule represents each individual’s unique genetic code.


    Restriction Fragment Length Polymorphisms (RFLPs)

    DNA restriction fragment analysis, or DNA fingerprinting, uses special proteins called restriction enzymes to cut up DNA. A specific restriction enzyme will only cut the DNA when it encounters a certain combination of nucleotides. This results in lengths of DNA, called restriction fragment length polymorphisms (RFLPs). For each individual, the size of these fragments is unique, like the person's DNA.

    RFLPs and Electrophoresis

    When DNA samples are taken from a suspect and crime scene, they are shipped to a lab and each exposed to the same array of restriction enzymes. Once the DNA is cut up, RFLPs from each sample are placed into small wells within a gel matrix, that looks much like a rectangular slab of Jell-o.

    This Jell-o-like slab containing the DNA is placed in an electrophoresis chamber which contains liquid and positive and negative electrodes. Current is then run through the chamber.

    DNA is negatively charged (-), and therefore attracted to anything that is positively charged (+). When current is run through the chamber, the DNA begins to migrate towards the positive pole. Large fragments will move through the gel more slowly than smaller fragments, and, after a short period of time, the RFLPs separate based on their size.

    dna testing

    Ultimately bands of DNA are visible in “lanes” that have moved straight out of each well. Each band in a lane represents many DNA fragments that are similar in size. Since the DNA from different individuals will have been cut at different places by the restriction enzymes, each person's DNA will form a unique pattern after being run through the gel.

    Comparison of DNA Fingerprints

    The electrophoresed DNA pattern of suspect and the pattern of samples obtained from the crime scene are then compared. If the crime scene samples contain RFLP patterns identical to those of the suspect a stong case can typically be made for the suspect’s involvement in the crime.

  • Psychological Profiling
  • As a branch of criminal science, psychological profiling is better known in practice than by name. Although no solid evidence can be obtained from this process, it provides an accurate way of guiding the direction, in which an investigation heads toward.
    What is Psychological Profiling?

    Psychological profiling involves investigating an offender's behaviour, motives and background in an attempt to further guide an investigation. Research shows that offender's that repeatedly rape or kill are driven by a heightened public fear for their actions and media attention, which could eventually lead to their arrest. Analysing the criminal's habits and rituals allows investigators to trace similarities between previous crimes. When these details of their lifestyle are made public, friends, neighbours and colleagues may recognize them.

    The Facts

    The process of psychological profiling began over a century ago, but was first distinctly used as a method in America during the 1950's. Investigators discovered through research, intriguing patterns and similarities between serial killer's behaviour. Some of the patterns discovered include the killers having suffered from child abuse as youngsters, whether it is sexual or physical and that this kind of abuse led to abnormal behaviours later on. As children and teenagers, they started fires, were cruel to animals or children and then in the late teenage years to early twenties, were engaging in petty crime and defying authority.

    Why Criminals Commit

    Committing serious crimes usually start at around the mid to late twenties. Being able to manipulate victims and show a sense of power and domination is a main drive for criminals, as well sexual motives. Murdering victims gives them the sense of success and control that they have never felt in their lives. Some criminals have also found that they need to relive that sense of victory that was felt during the committing of the crime, so they take something from their victims, for example, jewelry, clothing and even body parts.

    Inductive Profiling

    Investigators putting together a profile use either inductive or deductive approaches. Inductive profiling involves assuming that when a criminal commits a crime, he or she will have a similar background and motive to others who have committed a similar crime. An example of this is a re-offending rapist whose target are white women, is not likely to be black, because crimes of the past that have been similar to this one have rarely crossed racial lines. However, these statements have been questioned and have experienced a lot of publicised drawbacks.

    Deductive Profiling

    Deductive profiling involves a process that avoids generalisations and averages. This method involves intently studying suspects in extreme detail and adapting findings in which new evidence surfaces. A deductive profile is set up based on the offender's actions before, during and after committing the crime. For example, if the murderer used a makeshift weapon, investigators are then able to deduce that the crime was probably spontaneous. Another example involves serial murderers. Investigators are able to find out whether the murder was organized, which means that the killer carried out a planned, premeditated attack on a victim, or if the attack was disorganized, meaning that the murder was unplanned and the killer behaved in an uncertain way. Organised and planned killers often carry a tool kit containing duct tape and rope to bind their victims and gloves and a mask to hide their identity.

    Serial Killers

    Serial killers are also known to stick within their 'comfort zone', for example, their own neighbourhood, before traveling further as their sense of power and domination heightens. A serial killer often leaves behind a signature or trademark of their work that is usually unnecessary, but emotionally fulfills the killer. There are usually also similar aspects, which will link the crimes together, for eg. the method of murder or the victims may all have some form of similarity. Profilers use this to trace and link crimes committed earlier together. Serial Killers Top^ Serial killers are also known to stick within their 'comfort zone', for example, their own neighbourhood, before traveling further as their sense of power and domination heightens. A serial killer often leaves behind a signature or trademark of their work that is usually unnecessary, but emotionally fulfills the killer. There are usually also similar aspects, which will link the crimes together, for eg. the method of murder or the victims may all have some form of similarity. Profilers use this to trace and link crimes committed earlier together.

  • Ballistics
  • In forensic science ballistics, the study of motion, examines the dynamics, angular movement, and effects of projectile units such as bullets, missiles, and bombs. There are many applications of ballistics within a criminal investigation.

    Bullets that have been fired at the scene of any crime will be examined in the hopes of discovering several pieces of information. The actual bullets can identify what type of gun the criminal used and whether or not the firearm is connected to any other crime. The amount of damage a bullet has sustained upon hitting a hard surface can help determine approximately where the shooter was standing, what angle the gun was fired from, and when the gun was fired. Any residue on the bullet can be studied and compared to residue on the hand of a suspect, on the gun that was fired, or on any object that was close by when the firearm was used. This information helps researchers uncover the identity of the shooter. When the bullets are missing, the type of impact they made can lead investigators to ascertain what kind of bullet the criminal used, and therefore the type of gun as well.

    Studying the markings found on a bullet or the impact a bullet made on any surface can establish exactly which gun the criminal used. Every firearm produces a slightly different and unique pattern on the shell-casing it fires; the bullet will therefore imprint a distinct pattern upon anything it hits. Once scientists have identified these markings they can easily match them to the appropriate firearm.

    There are many experts deeply involved in this study, and they are frequently called upon to help solve crimes. Ballistics details are also commonly input into a large database that can be accessed by law enforcement agencies all across the country. When someone enters new data, the computer locates any relevant data from previous investigations. This information can lead to the discovery of the owner of a particular weapon, and assist in tracking down the guilty party who fired the gun.

  • Identikit
  • The Identikit system which was developed in the USA in the 1940s, used transparent layers to build up a picture of a suspect's face. Witnesses descriptions of eye colour, hair styles, etc, were laid over a basic face shape. Mordern developments include Photofit and computerised E-fit (Electronic Facial Identification Technique).

  • Surveillance

  • Crime-fighters increasingly use electronic methods to spy on suspects.They can plant bugs(hidden microphones and video cameras) and intercept telephone calls and computer data