DNA & Fingerprinting. By: Florina Altshiler, Esq. Russo & Toner, LLP

Transcription

1 DNA & Fingerprinting By: Florina Altshiler, Esq. Russo & Toner, LLP

2 DNA & Fingerprinting By: Florina Altshiler, Esq. Russo & Toner, LLP

3 What is DNA? DNA, or deoxyribonucleic acid, is the fundamental building block for an individual's entire genetic makeup. It is a component of virtually every cell in the human body. A person's DNA is the same in every cell ie. the DNA in a man's blood is the same as the DNA in his skin cells, semen, and saliva.

4 Where is DNA contained?

5 mucus perspiration fingernails urine blood semen skin cells tissue organs muscle brain cells bone teeth hair saliva

6 Common uses of DNA include... Forensic testing - to help identify suspects or victims in a criminal investigation Gene therapy - to test parents or fetuses for genetic conditions or birth defects Genetic genealogy - to find out more about someone's ancestry

7 Parental testing to establish if someone is the biological parent of a child

8

9 DNA collected from a crime scene will... Link a suspect to the evidence Eliminate a suspect Identify a victim through DNA from relatives, even when the body can not be found Evidence can be linked to the same perpetrator locally, statewide, and nationally

10

11 How is DNA collected? HOW IS DNA COLLECTED?

12 Biology Extremely small samples of DNA can be used as evidence DNA is first extracted from its biological source material Then measured to evaluate the quantity of DNA recovered (screening) After isolating the DNA from its cells, specific regions are copied with a technique known as the polymerase chain reaction, or PCR PCR produces millions of copies for each DNA segment of interest and thus permits very minute amounts of DNA to be examined Multiple STR regions can be examined simultaneously to increase the informativeness of the DNA test (testing)

13 Technology Resulting PCR products are separated and detected in order to characterize the STR region being examined. After detecting the STR alleles, the number of repeats in a DNA sequence is determined, a process known as sample genotyping. The specific methods used for DNA typing are validated by individual laboratories to ensure that reliable results are obtained and before new technologies are implemented. DNA databases are valuable tools and play an important role in law enforcement

14 DNA Contamination When DNA from another source gets mixed with DNA relevant to the case. Sneezes or coughs over the evidence Touches his/her mouth, nose, or other part of the face and then touches the area that may contain the DNA to be tested.

15 DNA Contamination cont... "PCR" replicates or copies DNA in the evidence sample Introduction of contaminants or other unintended DNA to an evidence sample can be problematic With such minute samples of DNA being copied, extra care must be taken to prevent contamination. If a sample of DNA is submitted for testing, the PCR process will copy whatever DNA is present in the sample; it cannot distinguish between a suspect's DNA and DNA from another source.

16 Chain of Custody A record of individuals who have had physical possession of the evidence Documentation is critical to maintaining the integrity of the chain of custody Maintaining the chain of custody is vital for any type of evidence. If laboratory analysis reveals that DNA evidence was contaminated, it may be necessary to identify persons who have handled that evidence. The fewer people handling the evidence = less chance of contamination for court admissibility hearings

17 Possible Results from DNA Testing

18 Inclusion Results obtained from the standard sample from a known individual are all consistent with or are all present in the results from the unknown crime scene sample = "match" Exclusion Results obtained from the standard sample from a known individual are not all present in the results from the unknown crime scene sample = nonmatch

19 Inconclusive Situations where no results or only partial results are obtained from the sample due to the limited amount of suitable human DNA OR Results are obtained from an unknown crime scene sample, but there are no samples from known individuals available for comparison

20 CODIS COMBINED DNA INDEX SYSTEM CODIS Unit manages the National DNA Index System (NDIS) It develops, provides, and supports the CODIS program to federal, state, and local crime laboratories to exchange and compare forensic DNA evidence from crime investigations. CODIS also provides support to: FBI advisory boards DOJ programs Legislation regarding DNA

21 How does CODIS work? Sexual assault case - evidence kit is collected from victim and DNA profile of the suspected perpetrator is developed from the swabs in the kit The forensic unknown profile attributed to the suspected perpetrator is searched against their state database of convicted offender and arrestee profiles contained within the Convicted Offender and Arrestee Indices (if that state is authorized to collect and database DNA samples from arrestees) Candidate match in the Convicted Offender or Arrestee Index -> the lab will go through procedures to confirm the match and, if confirmed, will obtain the identity of the suspected perpetrator.

22 The DNA evidence is also searched against the state s database of crime scene DNA profiles = the Forensic Index. Candidate match in the Forensic Index, lab goes through the confirmation procedures and, if confirmed, the match will link two or more crimes together The law enforcement agencies then share information obtained on each of the cases and develop leads

23 Hit in the database? CODIS was designed to compare a target DNA record against the DNA records contained in the database. Laboratories involved in the match exchange information to verify the match and establish coordination between agencies The match of the forensic DNA record against the DNA record in the database is used to establish probable cause to obtain a DNA sample from the suspect. Law enforcement agency uses documentation to obtain a court order authorizing the collection of a known biological reference sample from the offender. The casework laboratory can then perform a DNA analysis on the known biological sample so that this analysis can be presented as evidence in court.

24 The DNA Identification Act, 14132(b)(3) specifies the access requirements for the DNA samples and records allows disclosure only to: Criminal justice agencies for law enforcement identification purposes; Judicial proceedings; Criminal defense purposes, to a defendant, who shall have access to samples and analyses performed in connection with the case in which such defendant is charged; or If personally identifiable information is removed, for a population statistics database, for identification research and protocol development purposes, or for quality control purposes.

25 Sexual Assault Forensic Examiner (SAFE) Program

26 The Sexual Assault Reform Act (SARA) became effective in February, The law requires the establishment of sexual assault forensic examiner (SAFE) programs in hospitals designated as 24-hour centers of excellence. As a result of this legislation, the New York State Department of Health (NYSDOH) developed standards for approving SAFE hospital programs, approving programs that train individual SAFE examiners, and certifying individual SAFE examiners. DOH-approved SAFE programs and specifically trained health professionals ensure victims are provided with competent, compassionate and prompt care, while providing the most advanced technology associated with DNA and other sexual assault forensic evidence collection and preservation.

27 SAFE 24-hour Centers of Excellence The Department is required to designate SAFE 24-hour Centers of Excellence in all areas of the state to give as many state residents as possible ready access to SAFE programs. Applications from any general hospital licensed under Article 28 with an emergency department are considered. Hospitals with existing programs must apply for Department of Health designation as a SAFE Center of Excellence. Hospitals are required to provide a private room in or near the emergency department with access to a shower and accessible for the disabled. There are reporting and equipment requirements for hospital programs.

28

29 April New Medical Exam Policy Guidelines emphasize the rape victim s physical and emotional needs should take precedence over criminal justice considerations. Revised from those issued in 2004, are aimed at establishing voluntary standards for care when rape victims seek help at hospitals or other medical facilities. Standards are mandatory for practitioners in federal prisons or in the military. Rape victims will be offered emergency contraception or in cases where health professionals have moral objections information on how to immediately obtain the medication. Many women who are sexually assaulted want to report the rape to the authorities immediately, but some are reluctant to do so. In such cases, victims should be encouraged to have a forensic medical examination anyway, since the evidence can be used later on. Pressuring these victims to report may discourage their future involvement

30 The protocol offers detailed recommendations on how evidence should be collected; what equipment should be on hand; and the importance of a team approach that involves law enforcement officers, prosecutors and advocates, as well as specially trained nurses or other health professionals.

31 Health Care Professionals Responsibilities SAFE exams should represent their best work in every respect. They need to: Write legibly. If a case goes to court, it will help everyone if the documentation is clear: Actual documentation may be enlarged and presented to jurors If prosecutors can read the medical record, they may have less need to talk to you. Legibility can reduce the amount of time health care personnel must spend in court You may not have to testify in a grand jury if your record is well documented. Put the chief complaint in quotes: I was raped.

32 Document the examination comprehensively. Years and many SAFE exams later, a person likely won t remember the case as clearly, but it s the vivid details that can be pivotal when testifying in court. Do not leave sections of the medical record blank.

33 Fingerprints

34 Latent Fingerprints Prints that are not visible to the naked eye, but do exist.

35 These prints are created because the fingers have tiny outlets for the expulsion of sweat and these outlets pick up salts, oils and tiny particles of dirt along the way. You may think that your hands and fingers are clean but at any given time your fingers are picking up these tiny molecules in everyday life; a common means of picking up these tiny particles is the passing of paper from one individual to another. Paper can carry a thin film of dirt and sweat particles that are passed on.

36 How are Latent Prints Recovered? Latent prints are visualised using magnesium powder It is gently brushed over hard and shiny surfaces in order to illuminate them Prints then can be photographed or 'lifted' using a variety of different tapes A Scenes of Crime Officer (SOCO) will have an extensive selection of powders and brushes in their CSI kit (Crime Scene Investigation) The varying brushes provide different coverings of powders when 'dusting' for prints so that the print is covered sufficiently for display without distorting its appearance Chemicals can also be used. One chemical is Cyanoacrylate Found in ordinary super glue used on non-absorbent surfaces like glass fingerprint It releases a vapor that reacts to the salt and oil in the

37 Super Glue fumes on a glass bottle

38 Latent Print Recovery Iodine fuming method - uses iodine crystals that vaporise by sublimation when heated. These vapours combine with components on the latent print, making it visible. The print developed will fade, so must be photographed immediately once observable. Ninhydrin - a compound that reacts with the amino acids in the print to produce a purple colouring. Useful on porous surfaces such as paper, though is not useful on wetted items or silk finish surfaces. Aluminium powder - the most common method of developing latent prints. The fine powder is applied with a brush, after which it adheres to perspiration residues and body oil deposits, visualising the print. The Magna Brush can be used to apply magnetic-sensitive powder. As the brush has no bristles, the chances of the print being damaged are greatly reduced.

39 Paper treated with Ninhydrin reagent

40

41 It is imperative that when 'dusting' the crime scene for prints that only those individuals who are directly involved in the collating of information are present AND They are correctly adorned in protective clothing to reduce the risk of contamination to print and other trace evidence to be found there

42

43 Types of Prints

44 FINGERPRINTS HAVE GENERAL RIDGE PATTERNS FOR CLASSIFICATION: Divided into three classes: LOOP % OF POPULATION HAS LOOPS WHORL % WHORLS ARCH - 5% ARCHES

45 Arches Arches are the simplest type of fingerprints that are formed by ridges that enter on one side of the print and exit on the other. No deltas are present.

46 Loops Loops must have one delta and one or more ridges that enter and leave on the same side. These patterns are named for their positions related to the radius and ulna bones, i.e. the bone the loop opening is facing towards.

47 Whorls Whorls have at least one ridge that makes (or tends to make) a complete circuit. They also have at least two deltas. If a print has more than two deltas, it is most likely an accidental. Plain Whorl Central Pocket Whorl

48 Whorls Part II

49 Ridge Characteristics = Minutiae

50 Minutiae Line-unit, it exists as only one isle with a pore. Line-fragment. 2 or more line-units A beginning or ending line.

51 Minutiae Bifurcation, a splitting line. Eye, two lines splitting and meeting each other shortly after that. Hook, a short splitting line.

52 Minutiae Pores, details in number, shape and size. Line shape, the lines vary breadth. Scars, the lines can not recover anymore. Incipient ridges, between the papillary lines.

53 How are prints compared? Ridge Flow and Pattern The fingerprint expert will analyse the print in more detail looking at the actual flow of the ridges to determine if there is any discernable pattern type. Digit Determination They will consider any clues in the print that may indicate which finger, thumb or area of palm that could have left the impression. Pattern and digit determination allow the expert to prioritise those fingerprints to be compared. Features The expert will also look at the quality and clarity of the unique features and characteristics that are revealed in the print. Quality and Clarity At the conclusion of the analysis stage the fingerprint expert will have made a decision as to the suitability of the print for further examination.

54 Comparison The second stage of the process is comparison. Once the fingerprint officer has analysed the unknown mark and accumulated all the information possible it is then compared to a print on a fingerprint form.

55

56 Comparison of Patterns The overall fingerprint pattern does not have sufficient uniqueness to determine identification, and only functions to narrow the number of possibilities of donors. However, at this stage of the comparison, differences in pattern type may be sufficient to exclude the unknown mark from the print. Comparison of Ridge Characteristics If the patterns are found to be in agreement the comparison moves to the next level - the comparison of ridge characteristics'. The ridge features are examined to ascertain whether they are in the same position, in the same order and have the same relationship to each other with none in disagreement in both the known prints and unknown marks. This is known as the coincident sequence.

57 If any unaccountable disagreement is found the identity cannot be established and the known print will be discounted from the comparison process. However, if the initial sequences agree in both impressions, the expert will proceed to compare the relative position and location of further characteristics in both prints, all the time looking for any disagreement in the sequence of characteristics. The fingerprint expert will also be taking into account the unique features of the ridges themselves looking for agreement between any visible distinctive ridge edge shapes and minute detail. This process will continue until the expert is satisfied that the comparison process is complete.

58 What is DNA? DNA, or deoxyribonucleic acid, is the fundamental building block for an individual's entire genetic makeup. It is a component of virtually every cell in the human body. A person's DNA is the same in every cell ie. the DNA in a man's blood is the same as the DNA in his skin cells, semen, and saliva.

59 Where is DNA contained?

60 mucus perspiration fingernails urine blood semen skin cells tissue organs muscle brain cells bone teeth hair saliva

61 Common uses of DNA include... Forensic testing - to help identify suspects or victims in a criminal investigation Gene therapy - to test parents or fetuses for genetic conditions or birth defects Genetic genealogy - to find out more about someone's ancestry

62 Parental testing to establish if someone is the biological parent of a child

63

64 DNA collected from a crime scene will... Link a suspect to the evidence Eliminate a suspect Identify a victim through DNA from relatives, even when the body can not be found Evidence can be linked to the same perpetrator locally, statewide, and nationally

65

66 How is DNA collected? HOW IS DNA COLLECTED?

67 Biology Extremely small samples of DNA can be used as evidence DNA is first extracted from its biological source material Then measured to evaluate the quantity of DNA recovered (screening) After isolating the DNA from its cells, specific regions are copied with a technique known as the polymerase chain reaction, or PCR PCR produces millions of copies for each DNA segment of interest and thus permits very minute amounts of DNA to be examined Multiple STR regions can be examined simultaneously to increase the informativeness of the DNA test (testing)

68 Technology Resulting PCR products are separated and detected in order to characterize the STR region being examined. After detecting the STR alleles, the number of repeats in a DNA sequence is determined, a process known as sample genotyping. The specific methods used for DNA typing are validated by individual laboratories to ensure that reliable results are obtained and before new technologies are implemented. DNA databases are valuable tools and play an important role in law enforcement

69 DNA Contamination When DNA from another source gets mixed with DNA relevant to the case. Sneezes or coughs over the evidence Touches his/her mouth, nose, or other part of the face and then touches the area that may contain the DNA to be tested.

70 DNA Contamination cont... "PCR" replicates or copies DNA in the evidence sample Introduction of contaminants or other unintended DNA to an evidence sample can be problematic With such minute samples of DNA being copied, extra care must be taken to prevent contamination. If a sample of DNA is submitted for testing, the PCR process will copy whatever DNA is present in the sample; it cannot distinguish between a suspect's DNA and DNA from another source.

71 Chain of Custody A record of individuals who have had physical possession of the evidence Documentation is critical to maintaining the integrity of the chain of custody Maintaining the chain of custody is vital for any type of evidence. If laboratory analysis reveals that DNA evidence was contaminated, it may be necessary to identify persons who have handled that evidence. The fewer people handling the evidence = less chance of contamination for court admissibility hearings

72 Possible Results from DNA Testing

73 Inclusion Results obtained from the standard sample from a known individual are all consistent with or are all present in the results from the unknown crime scene sample = "match" Exclusion Results obtained from the standard sample from a known individual are not all present in the results from the unknown crime scene sample = nonmatch

74 Inconclusive Situations where no results or only partial results are obtained from the sample due to the limited amount of suitable human DNA OR Results are obtained from an unknown crime scene sample, but there are no samples from known individuals available for comparison

75 CODIS COMBINED DNA INDEX SYSTEM CODIS Unit manages the National DNA Index System (NDIS) It develops, provides, and supports the CODIS program to federal, state, and local crime laboratories to exchange and compare forensic DNA evidence from crime investigations. CODIS also provides support to: FBI advisory boards DOJ programs Legislation regarding DNA

76 How does CODIS work? Sexual assault case - evidence kit is collected from victim and DNA profile of the suspected perpetrator is developed from the swabs in the kit The forensic unknown profile attributed to the suspected perpetrator is searched against their state database of convicted offender and arrestee profiles contained within the Convicted Offender and Arrestee Indices (if that state is authorized to collect and database DNA samples from arrestees) Candidate match in the Convicted Offender or Arrestee Index -> the lab will go through procedures to confirm the match and, if confirmed, will obtain the identity of the suspected perpetrator.

77 The DNA evidence is also searched against the state s database of crime scene DNA profiles = the Forensic Index. Candidate match in the Forensic Index, lab goes through the confirmation procedures and, if confirmed, the match will link two or more crimes together The law enforcement agencies then share information obtained on each of the cases and develop leads

78 Hit in the database? CODIS was designed to compare a target DNA record against the DNA records contained in the database. Laboratories involved in the match exchange information to verify the match and establish coordination between agencies The match of the forensic DNA record against the DNA record in the database is used to establish probable cause to obtain a DNA sample from the suspect. Law enforcement agency uses documentation to obtain a court order authorizing the collection of a known biological reference sample from the offender. The casework laboratory can then perform a DNA analysis on the known biological sample so that this analysis can be presented as evidence in court.

79 The DNA Identification Act, 14132(b)(3) specifies the access requirements for the DNA samples and records allows disclosure only to: Criminal justice agencies for law enforcement identification purposes; Judicial proceedings; Criminal defense purposes, to a defendant, who shall have access to samples and analyses performed in connection with the case in which such defendant is charged; or If personally identifiable information is removed, for a population statistics database, for identification research and protocol development purposes, or for quality control purposes.

80 Sexual Assault Forensic Examiner (SAFE) Program

81 The Sexual Assault Reform Act (SARA) became effective in February, The law requires the establishment of sexual assault forensic examiner (SAFE) programs in hospitals designated as 24-hour centers of excellence. As a result of this legislation, the New York State Department of Health (NYSDOH) developed standards for approving SAFE hospital programs, approving programs that train individual SAFE examiners, and certifying individual SAFE examiners. DOH-approved SAFE programs and specifically trained health professionals ensure victims are provided with competent, compassionate and prompt care, while providing the most advanced technology associated with DNA and other sexual assault forensic evidence collection and preservation.

82 SAFE 24-hour Centers of Excellence The Department is required to designate SAFE 24-hour Centers of Excellence in all areas of the state to give as many state residents as possible ready access to SAFE programs. Applications from any general hospital licensed under Article 28 with an emergency department are considered. Hospitals with existing programs must apply for Department of Health designation as a SAFE Center of Excellence. Hospitals are required to provide a private room in or near the emergency department with access to a shower and accessible for the disabled. There are reporting and equipment requirements for hospital programs.

83

84 April New Medical Exam Policy Guidelines emphasize the rape victim s physical and emotional needs should take precedence over criminal justice considerations. Revised from those issued in 2004, are aimed at establishing voluntary standards for care when rape victims seek help at hospitals or other medical facilities. Standards are mandatory for practitioners in federal prisons or in the military. Rape victims will be offered emergency contraception or in cases where health professionals have moral objections information on how to immediately obtain the medication. Many women who are sexually assaulted want to report the rape to the authorities immediately, but some are reluctant to do so. In such cases, victims should be encouraged to have a forensic medical examination anyway, since the evidence can be used later on. Pressuring these victims to report may discourage their future involvement

85 The protocol offers detailed recommendations on how evidence should be collected; what equipment should be on hand; and the importance of a team approach that involves law enforcement officers, prosecutors and advocates, as well as specially trained nurses or other health professionals.

86 Health Care Professionals Responsibilities SAFE exams should represent their best work in every respect. They need to: Write legibly. If a case goes to court, it will help everyone if the documentation is clear: Actual documentation may be enlarged and presented to jurors If prosecutors can read the medical record, they may have less need to talk to you. Legibility can reduce the amount of time health care personnel must spend in court You may not have to testify in a grand jury if your record is well documented. Put the chief complaint in quotes: I was raped.

87 Document the examination comprehensively. Years and many SAFE exams later, a person likely won t remember the case as clearly, but it s the vivid details that can be pivotal when testifying in court. Do not leave sections of the medical record blank.

88 Fingerprints

89 Latent Fingerprints Prints that are not visible to the naked eye, but do exist.

90 These prints are created because the fingers have tiny outlets for the expulsion of sweat and these outlets pick up salts, oils and tiny particles of dirt along the way. You may think that your hands and fingers are clean but at any given time your fingers are picking up these tiny molecules in everyday life; a common means of picking up these tiny particles is the passing of paper from one individual to another. Paper can carry a thin film of dirt and sweat particles that are passed on.

91 How are Latent Prints Recovered? Latent prints are visualised using magnesium powder It is gently brushed over hard and shiny surfaces in order to illuminate them Prints then can be photographed or 'lifted' using a variety of different tapes A Scenes of Crime Officer (SOCO) will have an extensive selection of powders and brushes in their CSI kit (Crime Scene Investigation) The varying brushes provide different coverings of powders when 'dusting' for prints so that the print is covered sufficiently for display without distorting its appearance Chemicals can also be used. One chemical is Cyanoacrylate Found in ordinary super glue used on non-absorbent surfaces like glass fingerprint It releases a vapor that reacts to the salt and oil in the

92 Super Glue fumes on a glass bottle

93 Latent Print Recovery Iodine fuming method - uses iodine crystals that vaporise by sublimation when heated. These vapours combine with components on the latent print, making it visible. The print developed will fade, so must be photographed immediately once observable. Ninhydrin - a compound that reacts with the amino acids in the print to produce a purple colouring. Useful on porous surfaces such as paper, though is not useful on wetted items or silk finish surfaces. Aluminium powder - the most common method of developing latent prints. The fine powder is applied with a brush, after which it adheres to perspiration residues and body oil deposits, visualising the print. The Magna Brush can be used to apply magnetic-sensitive powder. As the brush has no bristles, the chances of the print being damaged are greatly reduced.

94 Paper treated with Ninhydrin reagent

95

96 It is imperative that when 'dusting' the crime scene for prints that only those individuals who are directly involved in the collating of information are present AND They are correctly adorned in protective clothing to reduce the risk of contamination to print and other trace evidence to be found there

97

98 Types of Prints

99 FINGERPRINTS HAVE GENERAL RIDGE PATTERNS FOR CLASSIFICATION: Divided into three classes: LOOP % OF POPULATION HAS LOOPS WHORL % WHORLS ARCH - 5% ARCHES

100 Arches Arches are the simplest type of fingerprints that are formed by ridges that enter on one side of the print and exit on the other. No deltas are present.

101 Loops Loops must have one delta and one or more ridges that enter and leave on the same side. These patterns are named for their positions related to the radius and ulna bones, i.e. the bone the loop opening is facing towards.

102 Whorls Whorls have at least one ridge that makes (or tends to make) a complete circuit. They also have at least two deltas. If a print has more than two deltas, it is most likely an accidental. Plain Whorl Central Pocket Whorl

103 Whorls Part II

104 Ridge Characteristics = Minutiae

105 Minutiae Line-unit, it exists as only one isle with a pore. Line-fragment. 2 or more line-units A beginning or ending line.

106 Minutiae Bifurcation, a splitting line. Eye, two lines splitting and meeting each other shortly after that. Hook, a short splitting line.

107 Minutiae Pores, details in number, shape and size. Line shape, the lines vary breadth. Scars, the lines can not recover anymore. Incipient ridges, between the papillary lines.

108 How are prints compared? Ridge Flow and Pattern The fingerprint expert will analyse the print in more detail looking at the actual flow of the ridges to determine if there is any discernable pattern type. Digit Determination They will consider any clues in the print that may indicate which finger, thumb or area of palm that could have left the impression. Pattern and digit determination allow the expert to prioritise those fingerprints to be compared. Features The expert will also look at the quality and clarity of the unique features and characteristics that are revealed in the print. Quality and Clarity At the conclusion of the analysis stage the fingerprint expert will have made a decision as to the suitability of the print for further examination.

109 Comparison The second stage of the process is comparison. Once the fingerprint officer has analysed the unknown mark and accumulated all the information possible it is then compared to a print on a fingerprint form.

110

111 Comparison of Patterns The overall fingerprint pattern does not have sufficient uniqueness to determine identification, and only functions to narrow the number of possibilities of donors. However, at this stage of the comparison, differences in pattern type may be sufficient to exclude the unknown mark from the print. Comparison of Ridge Characteristics If the patterns are found to be in agreement the comparison moves to the next level - the comparison of ridge characteristics'. The ridge features are examined to ascertain whether they are in the same position, in the same order and have the same relationship to each other with none in disagreement in both the known prints and unknown marks. This is known as the coincident sequence.

112 If any unaccountable disagreement is found the identity cannot be established and the known print will be discounted from the comparison process. However, if the initial sequences agree in both impressions, the expert will proceed to compare the relative position and location of further characteristics in both prints, all the time looking for any disagreement in the sequence of characteristics. The fingerprint expert will also be taking into account the unique features of the ridges themselves looking for agreement between any visible distinctive ridge edge shapes and minute detail. This process will continue until the expert is satisfied that the comparison process is complete.