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CSI: The Science of:

Terms in this set (14)

A fingerprint in its narrow sense is an impression left by the friction ridges of a human finger. The recovery of fingerprints from a crime scene is an important method of forensic science. Fingerprints are easily deposited on suitable surfaces (such as glass or metal or polished stone) by the natural secretions of sweat from the eccrine glands that are present in epidermal ridges. These are sometimes referred to as "Chanced Impressions".
In a wider use of the term, fingerprints are the traces of an impression from the friction ridges of any part of a human or other primate hand. A print from the sole of the foot can also leave an impression of friction ridges.
Deliberate impressions of fingerprints may be formed by ink or other substances transferred from the peaks of friction ridges on the skin to a relatively smooth surface such as a fingerprint card. Fingerprint records normally contain impressions from the pad on the last joint of fingers and thumbs, although fingerprint cards also typically record portions of lower joint areas of the fingers.
Human fingerprints are detailed, presumed to be nearly unique, difficult to alter, and durable over the life of an individual, making them suitable as long-term markers of human identity. They may be employed by police or other authorities to identify individuals who wish to conceal their identity, or to identify people who are incapacitated or deceased and thus unable to identify themselves, as in the aftermath of a natural disaster. Fingerprint analysis, in use since the early 20th century, has led to many crimes being solved. This means that many criminals consider gloves essential. In 2015, the identification of gender by use of a fingerprint test has been reported.
Fingerprint identification, known as dactyloscopy, or hand print identification, is the process of comparing two instances of friction ridge skin impressions (see Minutiae), from human fingers or toes, or even the palm of the hand or sole of the foot, to determine whether these impressions could have come from the same individual. The flexibility of friction ridge skin means that no two finger or palm prints are ever exactly alike in every detail; even two impressions recorded immediately after each other from the same hand may be slightly different. Fingerprint identification, also referred to as individualization, involves an expert, or an expert computer system operating under threshold scoring rules, determining whether two friction ridge impressions are likely to have originated from the same finger or palm (or toe or sole).
An intentional recording of friction ridges is usually made with black printer's ink rolled across a contrasting white background, typically a white card. Friction ridges can also be recorded digitally, usually on a glass plate, using a technique called Live Scan. A "latent print" is the chance recording of friction ridges deposited on the surface of an object or a wall. Latent prints are invisible to the naked eye, whereas "patent prints" or "plastic prints" are viewable with the unaided eye. Latent prints are often fragmentary and require the use of chemical methods, powder, or alternative light sources in order to be made clear. Sometimes an ordinary bright flashlight will make a latent print visible.
When friction ridges come into contact with a surface that will take a print, material that is on the friction ridges such as perspiration, oil, grease, ink or blood, will be transferred to the surface. Factors which affect the quality of friction ridge impressions are numerous. Pliability of the skin, deposition pressure, slippage, the material from which the surface is made, the roughness of the surface and the substance deposited are just some of the various factors which can cause a latent print to appear differently from any known recording of the same friction ridges. Indeed, the conditions surrounding every instance of friction ridge deposition are unique and never duplicated. For these reasons, fingerprint examiners are required to undergo extensive training. The scientific study of fingerprints is called dermatoglyphics.
It is the identification of any person by testing their blood. The Testing is by identifying a person's DNA (or Deoxyribonucleic Acid). Any Set of our body (which is made up of cells) does contains DNA. 99.9% of the DNA from two people will be identical. The 0.1% of DNA code sequences that vary from person to person are what make us unique. These sequences are called genetic markers, and are the part of the code that forensic scientists use when doing a DNA test. Identical twins are the only people who have identical genetic markers. However, the more closely related two people are, the more likely it is that some of their genetic markers will be similar. The key to DNA testing is knowing where to look in the billions of letters of genetic code to find the genetic markers that will identify the important similarities or differences between people. Parental, forensic and genetic testing look for similarities in the genetic markers between two biological samples. Because all cells in the body contain exactly the same DNA, samples can be taken from almost anywhere in the body, including skin, hair follicles, blood and other bodily fluids. A forensic scientist might be asked to compare DNA from skin cells found underneath the fingernails of an attack victim, with the DNA from a blood sample taken from a potential suspect. First of all, the DNA is isolated from the cells and millions of copies are made, using a method called 'polymerase chain reaction', or PCR.PCR uses a naturally occurring enzyme to copy a specific stretch of DNA over and over again. Having lots of DNA makes the genetic code easier to analyse. The DNA molecules are then split at particular locations to separate them into known 'chunks' and the code at those specific points is analysed to create a DNA fingerprint. The fingerprints from the two different samples are then compared to see if they match. The accuracy of DNA tests has big implications. DNA tests are sometimes the only evidence to prove that a suspect was involved in a crime, or free someone who has been wrongly convicted. It is easy to tell if DNA from two biological samples does not match. But a match doesn't make you totally certain that the two samples come from the same person. There is always a small chance that two different people's genetic markers could be the same, especially if they are related. To reduce the chance of error, scientists test more than one genetic marker. The more identical markers there are in two samples, the more accurate the test. However, testing more markers takes more time and is more expensive. Forensic DNA tests usually examine six to ten markers. The chances that two unrelated people have identical profiles is less than one in one billion.
Blood Splatter Analysis inolves the study and analysis of bloodstains at a known or suspected violent crime scene with the goal of to helping investigators draw conclusions about the nature, timing and other details of the crime.
The use of bloodstains as evidence is not new; however, the application of modern science has brought it to a higher level since the 1970s and '80s. New technologies, especially advances in DNA analysis, are available for detectives and criminologists to use in solving crimes and apprehending offenders.
Calculating the speed at which drops of blood leave the body during an attack is an important measurement for blood pattern analysis. The physics behind the velocity and size of a blood drop gives investigators an idea of what kind of wound was inflicted.
A drop of blood falling from a cut finger, for instance, is a battle primarily between the force of surface tension, which keeps it stuck to the body, and gravity, which pulls it downwards. Solve the equations, and you'll find that a typical drop released this way has a volume of less than one percent of a teaspoon. Blood released from a wound by a violent impact -- such as a bullet -- tends fly in even smaller drops. That's because the force of a bullet is much stronger than gravity and easily overcomes the surface tension, flinging tiny drops away at high speeds.
Blood contains three components or blood cells that are suspended within plasma. The three components are erythrocytes, leukocytes, and platelets, Because plasma is less dense than the blood cells, it can be easily separated. Plasma does not separate from blood cells whilst circulating in the bloodstream because it is in a constant state of agitation. Upon exiting the body, bloodstains transit from bright red to dark brown, which is attributed to oxidation of oxy-hemoglobin (HbO2) to methemoglobin (met-Hb) and hemichrome(HC). The fractions of HbO2, met-Hb and HC in a bloodstain can be used for age determination of bloodstains and can be measured by Reflectance Spectroscopy.
In Ancient Egypt (3000 BC), Mummification was an example of Autopsy. In modern Times Autopsy is done in a quite different way, The procedure of Autopsy we use today was Standarised by Rudolph Virchow in the 20th Century. We have got two types of Autopsies: 1) Forensic- Which is medical-legal and spends almost as much time on the Internal Part of the body as on the External , 'cause that's where evidence is'. Forensic Autopsies try to find out answers for the cause of death as a part of overall police investigation.2) Clinical - In this the cause of death is found out for Research and Study Purposes. if the autopsy reveals a natural disease process such as leukemia or cancer, then the death would be considered natural. But when that evidence is added to the police report that states the body was found next to an ice-covered, fallen ladder, the manner of death is an accident. It would be easy to assume a gunshot wound is the result of a homicide. an autopsy could reveal that the wound patterns, angle of bullet entry and gun powder residue indicate that the gun was fired while being held by the victim. The wounds are self-inflicted, so that would be ruled a suicide.
Its Process is as follows:
The First step is External Examination, In this we first Handle, Clean and Move the body which is termed as diener. After that Ultraviolet rays might be used to search bod surfaces for any evidences. Samples such as Nails, Hairs etc. might be radio graphically imaged. After that the Wounds are Examined. Than the Body is weighed on a scale which is designed to accommodate the Container of the Body as well.
The Second step is Internal Examination, In this first of all a plastic/rubber brick called a body block is placed under the back of the body. The Internal Examination consists of inspecting the internal organs of the body for evidence of Trauma or other indications for the cause of Death.Patholgists have a variety of ways of Examining the rest of the body to collect evidences etc.If they want to preserve something, In many cases the Brain , they do so in Formalin [15% Formaldehyde(also part of last year's curriculum) gas in buffered water].
: I read more than a few Articles about this and All I was able to take out is : Investigators conduct informal crime scene reconstruction while processing, documenting, and collecting evidence. This process is often subconscious. The formal, second phase of crime scene reconstruction is a conscious process. It takes place after the processing of the scene, analysis of the evidence, and completion of all investigative processes. The methodology for crime scene reconstruction needs standardization for it to mature. The scientific method is a proven systemic process of problem-solving that follows six steps. These steps are to state the problem, develop a hypothesis regarding the explanation or solution of the problem, test the hypothesis by experimentation, form a theory, use theories to predict events, and consider as a scientific law a theory that holds up under testing as an accurate predictor. The hypothesis in crime scene reconstruction needs to be narrow in scope and precise. The investigator must give equal emphasis to all feasible and reasonable possibilities when considering answers to questions. Opinions must rest on an analysis of the physical evidence and known facts. Results must be reviewable, testable, and repeatable. In addition, opinions are always open to new knowledge. The use of the scientific method can overcome obstacles to the admission of testimony. The analysis concludes that a decision template is an appropriate format for applying the scientific method to reconstruction in that it guides the process and documents the analysis.
It is the application and study of insect and other arthropod biology to criminal matters. It also involves the application of the study of arthropods, including insects, arachnids, centipedes, millipedes, and crustaceans to criminal or legal cases. It is primarily associated with death investigations; however, it may also be used to detect drugs and poisons, determine the location of an incident, and find the presence and time of the infliction of wounds. Forensic entomology can be divided into three subfields: urban, stored-product and medico-legal/medico-criminal entomology. It has been written about even in Sun Tzu's Works (Part of 2014 WSC Curriculum). The SEM (Scanning Electron Microscopy) method is effective provided there is ample time and the proper equipment and the particular fly eggs are plentiful. The ability to use these morphological differences gives forensic entomologists a powerful tool that can help with estimating a post mortem interval, along with other relevant information, such as whether the body has been disturbed post mortem. In 2001, a method was devised by Jeffrey Wells and Felix Sperling to use mitochondrial DNA to differentiate between different species of the subfamily Chrysomyinae. This is particularly useful when working to determine the identity of specimens that do not have distinctive morphological characteristics at certain life stages. A valuable tool that is becoming very common in the training of forensic entomologists is the use of mock crime scenes using pig carcasses. The pig carcass represents a human body and can be used to illustrate various environmental effects on both arthropod succession and the estimate of the post mortem interval.
It is created when objects contact. Material is often transferred by heat or induced by contact friction.
The importance of trace evidence in criminal investigations was shown by Dr. Edmond Locard in the early 20th Century. Since then, forensic scientists use trace evidence to reconstruct crimes, and to describe the people, places and things involved in them. Studies of homicides published in the forensic science literature show how trace evidence is used to solve crimes. Trace evidence is important in accident investigation, where movement of one part against another will often leave a tell-tale mark. Such analysis is of great use in forensic engineering.
Examples of typical trace evidence in criminal cases include glove prints, hairs, cosmetics, Lipsticks, plant fibers, mineral fibers, synthetic fibers, glass, paint chips, soils, footprints, botanical materials, gunshot residue, explosives residue, and volatile hydrocarbons (arson evidence). For such evidence to be useful, it must be compared to similar items from suspects, but particular care is necessary to ensure a thorough analysis. Analysis of trace materials most often begins with a visual examination of the evidence usually involving macrophotography. This is then usually followed by microscopic analysis, of which a number of different types are available depending on the type of material to be analysed, such as a stereomicroscope, scanning electron microscope (SEM) or comparison microscope. SEM is especially useful because X-ray analysis can be conducted on selected areas of the sample, so is a form of microanalysis. It is useful where chemical residues can show unusual elements present which may indicate chemical attack of the product. A car accident caused by a diesel fuel leak, for example, showed traces of sulphur on the cracked tube indicative of attack by sulfuric acid from the battery.
Gunshot residue may be identified by elemental analysis using atomic absorption or with a scanning electron microscope equipped with an energy dispersive spectroscope. Small amounts of explosives, volatile hydrocarbons, and other chemicals are identified with the use of analytical instruments, such as gas chromatography, mass spectrometry, and infrared spectroscopy, all of which separate out the components of the chemicals.
Similar comments apply to damaged items from an accident scene, but care is needed in ensuring that the sample is not damaged by the testing, or sampling for testing. Such nondestructive testing must always be used first before considering destructive methods which involve taking small samples from the item for more detailed tests, such as spectroscopic analysis. Use of all such methods must be done in consultation with other experts and the relevant authorities, such as lawyers on both sides of a case.
It is the study and examination of bodily fluids that is used in forensic science as a means of segregating fluids excreted by assailants or attackers in varying criminal acts. These acts can range from physical assault to sexual assault, right through to the act of murder and all of them will have an element of fluid secretion attached to them. Serology allows the forensic scientists to segregate these bodily fluids when found at the scene of the crime and then perform a variety of tests on them in order to identify where these fluids originated from - or most importantly - who they came from.
One important aspect of Serology is determining whether or not stains resembling blood found at a crime scene are actually blood or some other stain that bears a similar resemblance.
Serology is split into two categories of investigation:
Presumptive Testing: These tests provide two separate means of producing a result. One is to use compounds that can have an effect on blood when introduced to it. These results are a simple and quick way of proving that samples are actually blood especially if time is of the essence.
Confirmatory Tests: This is a more involved set of tests that are carried out using samples of what is believed to be blood and mixing them with a chemical compound that reacts adversely with haemoglobin, the resultant factor being the production of crystals under the microscope that can be identified as blood.
It is important that these tests - either one of them - are carried out to prove that these stains are in actual fact blood; and, more importantly, human blood. This is particularly important if the deceased's body has been found outside where it may be possible that animal blood has been spilled on the ground at some point.


Serology, in addition to examining and identifying blood, is used to identify and categorise semen, saliva, sweat and even human faeces. This can be achieved in the instance of faeces as it is covered in a mucus membrane to enable expulsion from the body.
Serology also has a use in proving if unlawful sexual intercourse has taken place; this has become a necessary element of forensic science given the rise in sexual assaults and cases of rape. The processes used by a Serologist can help time intercourse and also help prove that unlawful intercourse actually took place.
It is important to note that although a large percentage of the population are classed as 'secretors' there are a smaller percentage of people who are non-secretors. Secretors exhibit elements of their blood's protein when they secrete other bodily fluids whilst non-secretors will not have levels of protein from their blood in their bodily fluids.
Testing the bodily fluids of secretors will reveal a result but non-secretors make it difficult for Serologists to gain any results so blood from these individuals must be tested in order to provide any level of positive result.
Again it is important to note that these procedures are used when other means of identification yield no results and although these tests may prove accurate other means of identification should be used, leaving this kind of scientific evidence to provide additional weight to any legal proceedings.
is an investigative tool used by law enforcement agencies to identify likely suspects (descriptive offender profiling) and analyze patterns that may predict future offenses and/or victims (predictive offender profiling). Offender profiling dates back to 1888 and the spree of Jack the Ripper, and the profiling theory describes how profiling will ideally work.[2] Current applications include predictive profiling, sexual assault offender profiling, and case linkage (using profiling to identify common factors in offenses and to help with suspect identification).
Goals of criminal profiling include providing law enforcement with a social and psychological assessment of the offender; providing a "psychological evaluation of belongings found in the possession of the offender" (p. 10); and offering suggestions and strategies for the interviewing process. Ainsworth (2001) identified four main approaches to offender profiling: geographical, investigative psychology, typological, and clinical profiling.
Five steps in profiling include analyzing the criminal act and comparing it to similar crimes in the past, an in-depth analysis of the actual crime scene, considering the victim's background and activities for possible motives and connections, considering other possible motives, and developing a description of the possible offender that can be compared with previous cases. Notable profilers in history include Walter C. Langer, James Brussel, Howard Teten, Robert Keppel and Richard Walter, John Douglas and Robert Ressler, and David Canter.
Entertainment media has depicted the practical use of offender profiling through television shows such as Law & Order: Criminal Intent, Profiler, Criminal Minds, Criminal Minds: Suspect Behavior, and the 1991 film The Silence of the Lambs. Unlike these and other popular media portrayals, offender profiling is just one of the tools, investigative methods, and techniques available to law enforcement personnel. Offender profiling is still controversial and subject to debate and varied opinions about the accuracy of, effectiveness of, evidentiary support for, and scientific validity and reliability of this investigative tool.