DNA Fingerprinting

In criminal cases, it is the strength of the evidence against the accused that determines the outcome of the case. This is why prosecutors try their best to come up with the strongest evidence to prove the guilt of the defendant, and this is also why defense lawyers try their best to discredit the evidence of the prosecution. To help them do this, both the defense and the prosecution solicits the help of experts in analyzing evidence and in proving the veracity of the evidences in the case. In recent times, the expert that lawyers have greatly depended on with regard to the analysis of evidence is the Forensic Expert who is capable of doing DNA profiling or fingerprinting.

DNA profiling

Forensic experts who do DNA profiling are able to identify the 0.1% difference between human DNA to be able to pinpoint if the DNA material found in a crime scene matches those of the accused. This process has been proven to be very accurate and it has even been used to resolve past cases, and in some instances, it has been able to exonerate some prisoners who have been found to be innocent of the crime they have been imprisoned for in the past.

The process

The process of DNA profiling involves a process by which DNA samples from a crime scene are collected from various sources such as hair and skin cells. The DNA will then be extracted from the samples and it would be cut using different enzymes that recognize the patterns in DNA. The DNA will then be made to run through a gel where they are separated by an electric current through a process called electrophoresis. The fragments would then be compared to the other samples to determine if there is a match. This process is highly accurate in identifying whose DNA material is found in a crime scene, but it cannot tell if a person has planted the DNA material, which is why authorities do not completely rely on DNA profiling.

In recent years, DNA profiling has been successful at helping both defense lawyers and prosecutors establish or dispute the veracity of evidence. This is because it provides an accurate way of establishing whether a suspect has been at a crime scene or if the DNA of the accused is found on the victim, which can establish guilt, especially in rape cases. However, DNA profiling should not be the sole basis of establishing guilt, as there is also the possibility of DNA material being planted by the real perpetrator of a crime.

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Biometric Controls - Why and How Fingerprints are Classified

Imagine the world without any hi-tech security. Will it be possible to survive? Today we have ?N? number of hi-tech security. In that very important and sensitive security system is Biometric Controls. Among all biometric techniques Finger Print identification is oldest and fruitful one, because no two persons have the hundred percent matching of their finger prints. Finger Prints matching is used by security departments and also in Forensic Department and also in civilian application area. All are in need of Finger Print matching process.

For this matching process some basic classification is needed. The prevalently recognized and mainly used classification is Edward Henry?s Classification. Before going into the types we will discuss some of the terms related to Finger Prints. The first one is core which is roughly the centre of fingerprints. Ridges are the lines in the finger print. Delta is a divergent which is either side of finger print and is created by bifurcation, or a dot, or a short ridge, or at the end of a ridge.

Henry?s Classification consists of three major types, Arch, Loop, and Whorl. Further these are classified as

I arch

1. Plain arch

2. Tented arch

II loop

1. Radial loop

2. Ulna loop

III whorl

1. Plain whorl

2. Central pocket loop

3. Double loops

4. Accidental

Plain Arch: Fingerprint patter in which the ridges enter on one side, rise in the middle and flow or tend to flow out from the other side, are called Plain Arch.

Tented Arch: Tented arch, has the same tendency to enter from one side and flow out from the other side, with the exception that the ridges from either an angle or an up thrust at the center. The impressions, with only two out of three characteristic of whorl pattern are classified as Tented Arch.

Loop: A loop is a type of fingerprint pattern in which one or more of the ridges enter on either side of the impression, recurve, touch or pass an imaginary line drawn from the delta to the core, and terminated or tend to terminate on or toward the same side of the impression from where such a ridges entered.

Any loop should have sufficient recurve; a delta and a ridge count across a looping ridge. Loops whose ridges flow towards radius bone (toward the thumb) are called Radial Loop, and those whose ridges flow in the direction of ulna bone (toward the little finger) are called Ulna Loops. Obviously, the two types of loop patterns change from left to right hand.

Plain Whorl: The patterns with at least two deltas and a recurve in front of each are called whorl types.

Any pattern, with at least two deltas and one recurving ridge, which may be a spiral, are any variation of a circle is called plain whorl. In any plain whorl an imaginary line drawn between the two deltas must touch are cross at least one of the recurving ridges with in the pattern area. However the presence of any appendage or spike may destroy the sufficient recurve.

Central pocket loop: In the central pocket loop (Fig-3.2.5), which has two deltas and at least a ridge making a complete circuit as in the plain loop, the imaginary line drawn between the two deltas must not touch any of the recurve ridges within the pattern area.

Double Loop: The double or twinned loop, consists of two deltas and two separate and distinct shoulders do not imply that ridges are disconnected.

Accidental whorl: The accidental is a pattern consisting of a combination of two or more types of patterns, with the exception of the plain arch, with two or more deltas; or a pattern, which does not belong to any of the other pattern classes. Unfortunately there are still a significant number of patterns, which cannot be classified into any of the above classes unambiguously. There are patterns in which the process of defining the focal points is not so obvious. Some times, multiplicity of selection of focal pints or spoilage of the sufficient recurve by the presence of a spike or an appendage may lead to error ness classification.

For verification we need the following properties

i) Universality ? everyone possesses the attributes
ii) Individuality ? The characteristic is different for everybody
iii) Stability ? the attributes remains invariant over lifetime
iv) Collectible (the characteristic is easy to capture)

Physical characteristic differ from person to person due to inherent individual genetic assortment within population and random processes affect the development of the embryo. With respect to their genetic formation, two individuals can be randomly close; a pessimistic assessment of identity discrimination based on biometrics may need to rely exclusively on an evaluation of diversity in the traits due to random process affecting human development.

Such an evaluation strategy would essentially rely on biometric samples from individuals who are identical similar in their genetic constitution. The extent of variation in a physical trait due to random development process differs from trait to trait. By definition identical twins cannot be distinguished based on DNA. Typically, most of the physical characteristics such as body type, voice, and face are very similar for identical twins and automatic verification based on face and hand geometry will fail to distinguish them. It is however, claimed that identical twins can be distinguished based on their fingerprints, retina, thermo gram, or iris patterns.

G.R. Brindha Shivakumar