How is fingerprinting used in forensic science

Working with fingerprint samples ranging in age from 0 to 28 years old, the VCU team found they could extract the most skin cells, and thus DNA, by pulling apart the fingerprint sandwich of tape and paper, cutting each layer into strips, and then immersing the strips in a solution designed to break open cell membranes and release the DNA.

These discoveries, as well as other recommendations, could have broader implications for improving the analysis of DNA from fingerprints in present-day investigations, Dawson Cruz says. That area of research is young—beginning in the late s—and forensic scientists are still working out the kinks.

As Dawson Cruz is looking to extract genetic information from aged prints, other researchers are looking to make better use of those smudges by examining other chemicals contained within.

The group first used these analyses to distinguish between samples from female and male sources; amino acid levels are known to be roughly twice as high in the sweat of females as in males. More recently, the researchers published work showing they could use the levels of metabolites in sweat to distinguish between samples from two different people, regardless of sex Anal. The advantage of the assays, he says, is that they can analyze samples at the crime scene more rapidly and cheaply than DNA testing.

So they could be used to determine quickly whether a particular print is from a man or woman or identify whether multiple people were present at a crime scene. The shortcoming, though, is that, unlike DNA, metabolite levels fluctuate according to age, activity level, and other factors, so the assays would be unable to pinpoint the identity of a suspect.

The assays can be run with less than a droplet of sweat, leaving the rest of the sample for later lab tests. The chemicals in fingerprints left on the outside of the package can offer clues. But the portable ion mobility spectrometry instruments that agents typically use to screen for explosives employ high temperatures to vaporize the chemicals in question and would destroy traditional fingerprint-lifting materials, like adhesive tape.

So if the package did turn out to be a bomb and agents had already screened the print for explosives via standard methods, its pattern would be too damaged to help track down who left it there. Staymates and colleagues wanted to develop a method that would analyze a fingerprint for chemical residues while preserving its pattern. After testing several combinations, they settled on a white Teflon strip paired with a high-temperature adhesive originally created for aerospace use.

They proved that it worked by creating prints with artificial fingers molded from ballistic gelatin that had been pressed into simulated plastic explosives Int. Ion Mobility Spectrom. Importantly, the print pattern stayed intact and could still be used for identification. And no other scientists had replicated their findings.

Research takes time, and Marcus Ray Johnson was running out of time. Miller testified that the team had been able to extract usable DNA from archived fingerprints as much as 20 years old.

Johnson was executed on Nov. There has long been a need in the forensic science community to research new ways to analyze crime-scene evidence, especially since , when the National Academy of Sciences published a report asserting that many forensic disciplines—fingerprint analysis included—have little or no scientific underpinning. The report drew a skeptical eye to a field in which validity had long been assumed rather than proved. The organization includes discipline-specific committees whose goal is to establish scientific standards that act to not only foster reliable results from existing forensic analysis techniques but also help vet new ones.

These efforts will help ensure forensic techniques are ready to stand up to the scrutiny of the courts and provide the best information possible. Related: Luminescent nanoparticles leave a glowing fingerprint. The first standards—including guides for fire investigation and drug identification—have been approved in the past few years.

Many others, including ones for fingerprint analysis, are still in the works. Contact the reporter. This assertion, however, is not based on any studies, research, or analysis.

In other words, there is no scientific basis for the belief that fingerprints are unique to each person. In fact, a high profile innocence case shows how wrong this assertion is. In , Brandon Mayfield, an attorney from Oregon, was arrested as a material witness by the FBI because his fingerprint matched a latent found at the scene of the Madrid train bombings.

The bombings killed people and injured hundreds more. The flow charts in the Forensic Science extract you have just read show the sequence of processes that forensic scientists go through when visualising latent fingerprints in blood on porous surfaces and latent fingerprints on non-porous surfaces. Charts like this are critically important for people trying to recover fingerprints from crime scenes. As you see, various different routes can be taken, depending mostly on the type of article being tested, and the tests must be used in the correct order until a sufficiently good print has been recorded.

If you were responsible for collecting fingerprint evidence at a major crime scene suggest what methods of visualisation you would choose if one of the likely objects for study was a small fragment of glass, not stained with blood or contaminated with grease. The protocols that can be followed for a small fragment of glass, such as from a mirror or window, are shown in Figure 4. The first step would be to make a visual examination and photograph the fragment step 1.

If the glass is dry, testing could proceed immediately; if not it would be necessary to let it dry at room temperature step 2. The glass could then be dusted with a fingerprint powder, such as aluminium powder, and photographed or lifted with special adhesive tape or gelatine lifters step 7 and p.

An alternative route, which might be taken since this is a major crime scene where the maximum information possible is needed, would be to shine a laser or high-intensity light on the sample and photograph any fluorescence visible step 3.

If this did not give a good record, then the next step would be to subject it to vacuum metal deposition with metallic zinc or gold, or both. The results of this experiment would also be photographed step 4.

Then the fingerprint powder would be used step 7. If the glass had needed drying, superglue fuming step 8 would probably not be a success. Similarly small particle reagent step 9 is unlikely to be successful since it is best used on wet or waxy surfaces. Grateful acknowledgement is made to the following sources for permission to reproduce material in this book.

Every effort has been made to contact the copyright holders. If any have been inadvertently overlooked the publishers will be pleased to make the necessary arrangements at the first opportunity.

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Print functionality varies between browsers. Printable page generated Sunday, 14 Nov , Forensic science and fingerprints Introduction This course covers how science can make fingerprints easier to study, how they are used in court and some of the questions about the extent to which fingerprint identification is sound and scientific.

Learning outcomes After studying this course, you should be able to: demonstrate knowledge and understanding of some of the basic facts, language, concepts and principles relating to the principles and significance of fingerprint matching demonstrate knowledge and understanding of some of the links between forensic science and the legal system draw together information from different sources and make logical deductions as a result demonstrate an understanding of how forensic scientists operate and use scientific evidence in a legal context.

Question 1 From your general knowledge, do you know what is special about fingerprints that makes them so useful to forensic science? Answer The skin on the ends of human fingers has ridges which form patterns that are unique to an individual. Question 2 What do forensic scientists mean by 'individualisation'?

Answer Individualisation is the process of unambiguously connecting a single individual or object to a crime scene. Activity 1: Looking at and taking fingerprints This activity should take from a few minutes up to an hour or so. If you have a magnifying glass or a hand-lens, you may like to look at each of your fingertips to see the range of patterns in the ridges. You may also like to look at those of another person in the same way and compare them with yours.

You may also find it interesting to take your own fingerprints and see what kind of features yours show. It can be messy and if you do not have an inkpad, you can buy kits for children that will suit your purposes very well. The kits can also contain dusting powder, brushes and notes on fingerprinting. Question 1 When is a fingerprint first formed in a person and how does it change throughout a life? What supports the assertion that no two fingerprints are identical?

Answer Fingerprints are formed in the foetus at about 28 weeks. They are formed of 'friction ridge skin' and so do not change throughout life and are maintained for some time after death. The most compelling evidence to date is that no two identical fingerprints have ever been found, despite there being probably hundreds of millions on file throughout the world.

Even identical twins who share the same DNA do not have identical fingerprints. Question 2 What are the three most common patterns in fingerprints? If a person had their fingerprints taken in in connection with a crime but was not charged or cautioned in connection with the offence, will their fingerprints be on the IDENT1 database? Why do you think that national fingerprint databases need to store 'print' sets of fingerprints, rather than one or two fingerprints? Answer The three basic ridge patterns are loops, arches and whorls.

After there was no need to remove a person's fingerprints from NAFIS, even if they were not cautioned. As the database has been carried forward unchanged to IDENT1, this does not necessarily mean that such a person's fingerprints will definitely be on the database but there is a good possibility that they will be on it.

As no two fingerprints are identical - even those on our own hands - all ten fingerprints must be on file if an individual fingerprint from a crime scene is to be connected to an individual. Answer The NAFIS system gave, and now IDENT1 gives, 15 potential matches and the relevant fingerprint expert then analyses all potential matches and states that either one or none of the matches is correct.

Case study 1 Shirley McKie: mistaken fingerprint evidence The very complex case of Scottish ex-police officer Shirley McKie shows some possible consequences for criminal justice if fingerprint attributions cannot be established to the satisfaction of both the defence and the prosecution. Figure 2 a Latent print found on a gift-tag at the crime scene, assigned to Asbury. The 16 matching characteristics are labelled in each print. Question 4 The technical details of the various fingerprint comparisons in the McKie and Asbury cases are beyond the scope of this course.

Answer First of all the expert will classify the major pattern as a loop, whorl, or arch. Case study 2 The Madrid bombings and the mistaken identification of Brandon Mayfield On 11 March a series of bombs devastated Madrid, Spain, killing people and wounding Figure 3 a Image of the fingerprint on the plastic bag that was found near the scene of the March Madrid bombings. Question 5 The old UK system of requiring 16 matching characteristics to establish identity between a crime scene print and a file reference print has now been abandoned and there is no quantitative standard.

Answer One particular reason for the change is that a mechanical match of the previous kind does not answer the question of whether there are points of difference discrepancies between the prints as well as the matches.

Figure 4 Fingerprint on a vehicle bonnet photographed and enhanced using the DCS-3 system. See text for details. Answer It is possible to use either a chemical reaction, usually one which produces a colour change, or to use light or another type of electromagnetic radiation to make the fingerprints visible. Figure 5 The electromagnetic spectrum. Question 7 Using the information in Figure 5 arrange the following types of radiation in order of increasing energy : infrared; ultraviolet; microwave; visible.

Answer Figure 5 shows that the wavelength of electromagnetic radiation decreases from radio waves, on the right of the figure to gamma rays, on the left of the spectrum. Question 8 Using Figure 5 , what is the approximate wavelength of the visible region of the electromagnetic spectrum and which regions lie on either side of it?

Answer The 'visible spectrum' is radiation with a wavelength of about nm and it lies between the infrared and the ultraviolet regions of the spectrum. Figure 6 Reflection of light. If white light is directed onto a blue material, all the wavelengths apart from blue are absorbed by the blue dye. The blue light is reflected. Question 9 If that coloured glass appears to you to be blue, what do think is happening to the daylight that is falling on it?

Answer All of the different wavelengths except blue are either absorbed or possibly reflected back and the blue light passes through - is transmitted - and is detected by your eyes, as shown in Figure 7 below.

Question 10 In order that they can emit blue light, which wavelengths will the optical brighteners need to absorb? Answer The absorbed light must have a shorter wavelength than visible blue light, which, from Figure 5 , is ultraviolet radiation.

Figure 7 Transmitted light. A transparent material appears blue by transmitted light when all wavelengths are absorbed except blue, which passes through the material.

Figure 8 A fingerprint on a mug has been made visible in fluorescent light. To see the fluorescence clearly it is necessary to work in a dark room using UV light. To avoid damage to eyes from the UV radiation, protective goggles need to be worn. Figure 9 The yellow stain on the stems of Agaricus xanthodermus damaged as they are pulled from the ground. Box 1 Some basic chemistry revised Atoms Atoms are the building blocks of all chemical substances.

Figure 10 The structural formula of water. Question 12 For the three reactions below, which of the equations are balanced chemical equations? Equation label: Equation 1. Equation label: Equation 2. Equation label: Equation 3. Answer Equations 1 and 3 are balanced, having equal numbers of C, H and O atoms on each side.

Acid-base reactions Acid-base reactions involve water, H 2 O. Question 13 The pH of the fluid in a human stomach varies between about 1 and 4. Answer The environment in our stomachs is very acidic. Any pH less than 7 is acidic.

Redox reactions The second kind of chemical reaction that is used extensively in forensic science, and analytical science in general, is the redox reaction. Equation label: Equation 5. Question 14 If an oxidation is loss of electrons, what do you think a reduction might be? Answer A reduction is where something gains electrons, such as that shown in Equation 6 where an aluminium ion is reduced to metallic aluminium. Equation label: Equation 6. By continuing to browse this site you agree to our use of cookies.

More info. Analyzing fingerprints left at the scene of a crime is one of the most critical parts of forensic analysis. The furrows and ridges present on your fingers, toes, and palms create a unique pattern.

Fingerprint analysis relies on this unique pattern, and forensic scientists will group patterns into the following distinct groups:. Loops: This pattern recurves on itself and forms a loop shape. This can be further divided into a radial loop that points towards the thumb or an ulnar loop that points towards the ulna bone.

Whorls: These are circular patterns similar to whirlpools. They can be plain or concentric whorls, a central pocket loop that is a loop with a whorl at one end, a double loop two loops in an S-shaped pattern , or an accidental loop that carries an irregular shape.

Arches: These are wave-like and consist of plain arches and bent arches that rise to a sharper point compared to plain arches. These patterns remain consistent with age.

Even in cases where new skin develops, it forms in the existing ridge and furrow patterns already established in the finger. In cases where the skin is damaged, the new skin also follows previous patterns. The above-mentioned patterns are used to include or exclude a fingerprint from the analysis. The fingerprint analyst uses specific points on the ridge to identify and compare similar points on an unknown fingerprint.

If a significant number of points correlate between the two fingerprints then they are said to be of the same person. Patent prints are collected using the standard manner of photography. The prints are photographed in high resolution using a forensic measurement scale.