INTRODUCTIONThe main area of criminal investigation is forensic science. It is very important to understand the forensic science first.
“Forensic science is the application of science to criminal and civil laws that are enforced by law enforcement in a criminal justice system” (Richard S. 2007, p. 5).
The criminal investigation is “collecting information and evidence to identify, locate and prosecute criminal suspects”. Professor Ralph F. Turner from Michigan State University prefers: “A criminal investigation is the reconstruction of the past event”. The definition can be clarified by examining the specific responsibilities of the researcher.
(James WO and Richard HW, 2000, p.5) This essay will demonstrate the brief history of the criminal investigation that will describe the crime lab, including its services. The purpose of this article describes criminal investigations before and now, becauseof the addition of new technologies (see Appendix 1.1).
Body PartThe DNA of an individual’s chromosomes controls a number of visible characteristics (Including race, color and sex) and invisible features (such as blood groups) and susceptibility to inherited diseases). The DNA is the same in all the cells of the body of an individual. It is almost certain that each person’s DNA is unique (unless you have one identical twins). However, current techniques allow us to examine only a small one total variation on individuals. The DNA structure is a double helix, in which two threads are twisted around. Other Each string consists of a linear series of predefined building blocks called nucleotides or bases. There are four basic types: adenine, thymine, cytosine and guanine, represented by the letters A , T , C and G.
The two chains are held together by between the bases. Adenine in one thread attracts the thymine in front of the flow, forming an A-T pair, and the cytosine draws only the guanine, forming a G-C pair. The base pairs form bridges between the two strands and are analogous to those of a spiral staircase. The sequence of the bases of one of the two lines constitutes the genetic code. The cell reads this code as a recipe. Income is substantially the same for all members of the same guy. In higher organisms, including humans, there is only a small part of this code. The vast majority of DNA in a cell does not have a known function, e.
This non-coding DNA varies a lot from one individual to another. It’s DNA which is examined in most DNA enhancement systems. Because highly variable and non-coding DNA regions are not associated. Any known characteristic it is not possible to obtain information on the individual by analyzing these regions. There are two important consequences of this. First of all, the development of DNA profiles is a comparative technique. The analysis of a bloodbath found on the scene of a crime tells us absolutely nothing about the author of the crime.
There are similarities between the crime scene profile and profile of a suspect indicating, where possible, the blood flow of dinner. Secondly, the collections of DNA profile that make up a library or a database can only be used in comparison with other DNA profiles. There is no information on individuals to whom. DNA profiles belonging to, or their relatives, can be obtained from this database.
The small and highly variable DNA areas are examined on different chromosomes. To the DNA section containing the chosen area must be identified. There are two main ones techniques that can be used for this: restriction fragment length polymorphism (RFLP).
Analysis (Wyman and White, 1980, Jeffreys et al, 1985, Baird et al, 1986) and Polymerase. Chain reaction (PCR) (Saiki et al, 1985). In the RFLP analysis, the long helix of DNA is cut into a series of fragments. This can be done with a series of specific enzymes called restriction endonucleases that cut DNA of all humans in specific points following the DNA base. Thus, a series of fragments is obtained, one of which contains the region of interest. This fragment is identified with a summary. A piece of synthetic DNA called a probe. The probe is designed in such a way that its basic sequence is (ie, forming A-T and G-C pairs with) the base sequence of either one it is part of the fragment of interest.
The probe looks for and attaches this fragment to the exclusion of all other fragments. The fragment to which the probe is connected can be detected. Addition of a chemical label (usually a radioactive atom) on the probe. The emitted radiation. The label creates a visible image of the X-ray film. The second way to identify the fragment of interest is to use the polymerase chain. The short and specific synthetic DNA molecules, called in the first place, are constructed in such a way that their basic sequences are complementary sequences of two zones, one at each end of the region of interest. The former are accompanied by the ends of this region of DNA .
The enzyme called polymerase used to make copies of the DNA segment of the before. In two hours you can make many copies, which can be easily detected and analyzed. This PCR capability allows you to limit a large number of copies. The amount of raw material is ideal for analyzing small amounts of blood or semen, and the fabric of decomposing remains in which most of the DNA is in poor condition (Hagelberg et al, 1991, Sykes, 1991, Jeffreys et al, 1992).
The most distinctive features of variable DNA fragments are the length (or the number of bases) and the basic sequence. There are already methods available to detect sequences differences, for example, in the HLA region (Saiki et al, 1989) and in mitochondrial DNA (Wrischnik et al, 1987, Vigilante et al, 1989, Sullivan et al, 1991). Sequence analysis. This is undoubtedly the way of the future (1) for writing forensic DNA. However, the most useful forensic DNA analysis systems that analyze differences in the length of particular fragments of an individual for. It has been discovered that these DNA regions contain multiple copies of a short DNA.
Sequence, repeated one after the other and attached forward (ie in tandem). Length The variation derives from different numbers of repetitions of nucleotide sequences. A region of DNA which contains a variable number of repetitions (2) in (3) tandem called VNTR site (Nakamura et al.
1987). A fragment in which the central sequence is repeated will be a hundred times clearer. More than one in which he repeats only ten times.
At least, in theory, any number of repetitions (Up to the maximum observed for this particular VNTR locus) may occur (4) to several. The length of the fragment can be measured (and, for PCR systems, the number of replicate) using electrophoresis to separate DNA fragments. Their lengths (5). In electrophoresis, DNA fragments pass through an agarose gel influence of an electric field. Shorter fragments move faster than longer fragments. Specific fragments of interest can be visualized using labeled probes (in RFLP analysis) or simply for coloring (for PCR products). The resulting model of fragments is called the DNA profile.
Different individuals rarely have similar patterns, especially when we combine RFLP. Results obtained from three or more different DNA regions (Risch & Devlin, 1992). Therefor, if the profiles of two different samples are similar, It is likely (but it is not they come from the same person. The probability increases because there are more areas of DNA examined. Currently, the Forensic Science State Laboratory database contains information on most RFLP analyze. This reflects the accumulation of five years of experience (6) with this type of DNA typing. In this method, the lengths of the fragments can be calculated by measuring positions in the profile.
This can be done using a tablet and a computer. To the resulting scanned profile can be stored in a computer database. Then you can search the database to match the profiles.
It’s done for several reasons. First of all, it indicates how common or rare a particular profile is. The strangest profile, more evidence comes from a person whose profile matches. Secondly, if samples taken from various crime scenes or victims have the same profile, it is likely that the same criminal is responsible. The DNA profile was used to connect together, some of the violations that George Kaufman finally pleaded guilty in 1989, the investigations of Armadale , Parkdale and Frankston violate those of Stephen Brown he pleaded guilty in 1993. The National Forensic Science Laboratory is currently active resources to allow the inclusion in the database of a large number of unresolved violations occurs every year.
It is expected that several serial crimes will be revealed from the recurrence of the same DNA profiles. Thirdly, the profile obtained at the scene of an unresolved crime can coincide with that of a person accused of a previous crime and whose profile has been registered (7) on the database. According to current Victorian legislation, the DNA profiles obtained by the suspects can only this database will be retained if the suspect is accused of a relevant offense within six months (or if a magistrate grants an extension of this period). The profile cannot be if the person is subsequently acquitted or successfully traveling against the conviction, and no blood samples are taken from criminals after their conviction. Fourthly, it is possible to establish a database on missing persons or their relatives, and search for profiles corresponding to those of unidentified bodies.
He also suggested it crew members and armed services must retain their DNA to help identification of victims of disasters or war (Weedn, 1991). It should be noted that the preparation of DNA profiles can help identify an organism only if DNA samples available for the deceased are available, the parents of the deceased or the wife and son of the deceased.Table 1 – Types of offence submitted for DNA profilingat the State Forensic Science Laboratory,Victoria, between 1 July 1989 and 30 June 1991Offence Number of cases Proportion of casesHomicide 25 15%Sexual offences 107 65%Other assaults 14 8%Burglary, robbery etc. 10 6%Miscellaneous 9 5%Total 165 Table 2 – Outcome of investigations in sexual offencecases analysed by DNA profiling(as at February 1993)Outcome Number of cases examined Proportion of casesSuspect discharged 21 22%Unsolved 19 20%Trial 21 22%Plea 31 32%Unheard 5 7%Not examined 10 Total 107 Table 3 – Outcome of criminal trials in sexual offenceVerdict Consent Identity TotalGuilty 7 5(a) 12Not guilty 6 3(b) 9Total 13 8 21Footnotes:a) No results were obtained from DNA profiling in 2 casesb) No results were obtained in all 3 of these cases.For Victoria, about two-thirds of all cases where the DNA profile was. Sexual crimes were used (Table 1). However, the DNA profile is only useful in the proportion of sexual offenses. Of the 621 cases of sexual crimes subjected to the state laboratory of forensic science in the two years from July 1989 to June 1991, They were analyzed using the DNA profile (Table 2) .
There are several reasons why some cases have been analyzed. In about 30% of cases, further examination was necessary (usually because no one was charged or they have been abandoned). In 30% of cases, a suitable sperm counter was not found. Most sexual offenses are provided with the consent and identification of the sperm source is. It’s not a problem. Sometimes the sperm sample cannot be linked to the crime.
Sperm stains were found on a blanket of a bed where an old widow said it had been violated by an intruder. A DNA profile of one of the points was different from the DNA profile of the suspect. The remains of the seminal points were delimited, then a third.
DNA profile, which did not coincide with the suspect or the first fundamental point. As a result, the coverage came from two other men. Further questions about the victim, in the end, it caused the information that they were sleeping in bed with their two daughters and in-laws several times in the past, and probably after the blanket has finally been washed. The suspect was involved in the attack of other tests. Among many paintings points for yours.
The monkeys, there was a blood stain. The DNA profile of the blood point corresponds to that of. The suspect was found guilty of aggravated assaults and violations. Ninety-seven sexual offenses in which the DNA profiles were performed during this period.
Period, approximately the same number of suspects were included and excluded. The place, in particular, comes from someone that is not suspecting , there is a very high the probability that the DNA profile shows the difference and excludes suspicion . Now widely used to investigate the police to identify suspects. In several cases, nine or more suspects have provided blood samples, and all, or. All but one of them was excluded.
It meant search costs and resources that have been redirected along other routes. Of the sexual offenses analyzed by the DNA profile, almost a third was convicted (Figure 2). The reasons for joining a culprit are not always several cases, they were found guilty after the presence of incriminating DNA tests before or in the commission procedure. 22% of cases underwent a complete test.
Most of these cases were on consent: identity was a problem in only 8 tests. In only three of these eight cases, DNA profiles provide a positive proof of a relationship between the accused and the offender (The results were not obtained in the other 5 cases) (Table 3). In some cases where the identity was in doubt in the test, sometimes the defense has challenged the admissibility of DNA tests (Roberts, 1993).
It was a defensive challenge confirmed by a judge in a single Supreme Court case where the state’s forensic science is. The laboratory intended to present DNA tests (R. v Lucas 2 V R. 109 (1992)). In 1989, the dismembered body of James Pinakos was found buried in two parcels on a beach. The blood stain was found in the house where the accused lived for several months when Pinakos disappeared.
It could not be a DNA profile obtained from the coloring of the blood compared to body tissue so that the latter was very decomposed. Nevertheless, the comparison of the DNA profiles of the deceased’s parents indicates that the bloodstain. It could come from one of your children. The defense has challenged the calculation of the probability of kinship with this case, and the prosecution decided. Remove probability estimates the judge then decided that it could not be DNA-proof has admitted that a jury would not be able to assess the importance of the between the bloodstain and the DNA profiles of the parents.From the Lucas case, several studies have shown the method of calculation.
Probability estimates of databases at the population level (Risch & Devlin , 1992 ; 1991 ; Evetts and Pinch, 1991 ; Devlin et al . 1990 , 1993 ; Balazs et al . 1990 , 1992 ; Chakraborty & Kidd , 1991 ; Buckleton et al . 1991 ) .
The state laboratory of forensic science has. Data on the population from DNA writing systems used at the laboratory, a representative. Victorian population sample (Gutowski et al, 1990). The laboratory has validated the criteria used to declare a coincidence or a misunderstanding between the profiles (Roberts et al, 1992) . Subsequently, three judges of the Victoria County Court and a Supreme Court.
The Queensland decided that the qualifications and knowledge of the forensic scientists of the state. The forensic laboratory in the field of demographic and genetics statistics is adequate. The courts have overwhelmingly accepted that DNA testing will be useful for a jury and they decided that a jury could correctly evaluate the weight of these tests (R v .
Gallienne , Victoria County Court , June 1992 ; R v . Soper, Queensland Supreme Court, . July 1992; R v. Percerep Victoria County Court, August 1992). ConclusionThis analysis shows that DNA tests are rarely crucial in the process.
To the main value of the DNA profile is in the early stages of a survey, before the process. It’s a powerful investigative tool to exclude people falsely suspected of involvement in a crime. It can provide a very strong evidence of participation, which is often sufficient to induce accused of pleading guilty or fighting the problem.