Comparison of Digital Fingerprinting and DNA Fingerprinting
Are digital fingerprints more reliable means of identification than DNA fingerprinting?
This scientific controversy report aimed to evaluate and compare the reliability of fingerprinting and DNA fingerprinting. Fingerprint identification is a method of identifying the unique patterns of human fingers which is advantageous for acquiring details of a person to identify them. DNA fingerprinting is a method used for identifying persons from their sample of DNA as the pattern of a DNA is unique for all individuals. Thus, main aims of this paper are to compare the reliability of fingerprint identification and DNA identification to establish which will be most effective for crime investigation. In addition to this, some loopholes for DNA fingerprinting have also been identified in the literature reports which include factors such as DNA coincidence, tampering, and error in identification. It is observed in this report that both latent, as well as DNA fingerprints are important for finding evidence in a crime scene but there are controversies in the use of both methods. In the case of DNA fingerprint, contamination of evidence can occur intentionally in a crime scene, forensic laboratory and by investigators. On the other hand, contamination of latent fingerprint can occur due to improper lifting methods, ineffective storage and packaging, and weather conditions. Thus, it is recommended to incorporate further studies and improved technology to increase reliability in both the techniques.
Forensic science plays a vital role in solving the crime by applying scientific methods and techniques which can demonstrate the guilt or innocence of a defendant in the criminal trial. Evidence such as Fingerprints and DNA (deoxyribonucleic acid) are useful in providing the link between suspect and victim at the crime scene and justice to innocent. Fingerprints were first, taken by William Herschel in 1858 and later Francis Galton identified the uniqueness and individuality which remain the same throughout the life. DNA fingerprinting was first described in 1985 by Alec Jeffrey and it is favourable in excluding suspects rather than establish the guilt. DNA profiling and digital fingerprint evidence are useful as they are strong, can identify the culprit and can be helpful in saving the innocent from a complex police investigation but at the same time both evidences have limitations where most scientists argue that DNA and fingerprints are fallible because of certain factors such as intentionally (cross-contamination) and unintentionally error (tampering, coincidence) occurrence. Although if both the evidence is not treated properly, then consequences will be a wrongful conviction, wrongful acquittal, and miscarriage of justice.
This review will examine the reliability and accuracy of both the evidence can be affected by contamination, contextual bias, scientific errors, CSI effect, collection and storage of sample in the laboratory process. DNA and fingerprints have proven its trustworthiness and reliability as a forensic tool for identifying evidence left at a crime scene. The aim of the review is to analyse the errors that jeopardize the reliability and accuracy of both. These can be identified and minimised by doing more research and providing education and training.
2. Evaluation, support, and science of DNA and fingerprint evidence
2.1 Fingerprint fundamentals
Numerous patterns can be found in the nature, form microscopic non-living organisms to singe living cells to the certain gigantic structures. The same thing is observed in the case of the fingerprint as well that naturally have the unique pattern formed due to friction. These fingerprint patterns are created by epidermal furrows (recessed) and ridges (raised). There are three common types of fingerprint patterns on the fingertips of humans. These three basic fingerprint patterns are arches, loops, and whorls. Arches are found 5% in the fingerprints 70% to 60% observed fingerprints have loop pattern and about 35% to 20% fingerprints that are observed to contain whorls pattern (Ifflab.org, 2018).
One unique characteristic that is beneficial in identification process is this that an individual’s fingerprints does not change over time and nor does it change with age. No two individuals can share a same fingerprint pattern, not even identical twins. Moreover, even the size of fingers increases with age, but still the fingerprint pattern remains the same (Trivedi 2015, p 69). Even a partial fingerprint of the culprit can be helpful in identifying the culprit and thus can be useful for the detectives.
Figure 1: Eight subcategories of the fingerprint pattern
Fundamental principles of Fingerprinting
In addition to the unique fingerprint pattern, there are three fundamental principles of fingerprint as well. These three fundamental principles include individual characteristic, unique pattern and remain unchanged.
1. Individual characteristics
In the first fundamental characteristics, the uniqueness of fingerprint pattern has been described. As per this principle, fingerprint is referred to as a unique characteristic of individual and no two individuals can have the same pattern of fingerprint (Song et al. 2015).
2. Remaining unchanged
According to this principle, throughout the lifetime of an individual, their fingerprints will remain unchanged. The fingerprint may get enlarged due to physical growth, but the pattern of one’s fingerprint will remain same throughout their lifespan (Nybom, Weising and Rotter 2014, p 01).
3. Unique patterns
The patterns of fingerprint may look complicated in first place, but their pattern is general and rigid. Because of this, it becomes easier for low enforcing people and forensic investigative to use a fingerprint as investigating tool which supports the third principal (Pahade & Kori 2015).
Figure 2: Fundamental principles of fingerprint
(Pahade & Kori 2015)
2.2 New tools and techniques which are making fingerprints more reliable
There are numerous top-level techniques and tools that are used for analysing fingerprint evidence. These tools and techniques have greater reliability and validity. Some of these tools and techniques include Alternate light source, cyanoacrylate processing and chemical development (Passari et al. 2015, p 68).
Alternate light source (ALS)
The tool of Alternate Light Source is widely used by forensic investigators to examine any surface where fingerprints of the suspect can likely be found. This tool either uses LED light or laser light that imitate web length of a frequency, or defined spectrum.
Figure 3: Using alternate light and fluorescent dye for making fingerprints clearly visible
(Source: Forensicsciencesimplified.org, 2018)
Another process that is often adopted by investigators is Cyanoacrylate processing which is also referred to as fuming. Fuming is done on a surface containing fingerprint with the application of dye stains and powders. The technique of Cyanoacrylate is performed on surfaces that are non-pours in nature (Zoppis et al. 2014).
Figure 4: Fumes of super glue adhering latent fingerprint
(Source: Zoppis et al. 2014)
On contrary to cyanoacrylate, the technique of observing fingerprints through chemical development is used when a surface is porous in nature. The pour surface on which chemical development of fingerprint is applied includes paper or cloths. The chemical ninhydrin makes the paint residues purple in colour thus making the fingerprints easy to be photographed. In addition to ninhydrin, DFO that is (1,2 diazafluorene 9 one) is also used for the same purpose (Nybom, Weising & Rotter, 2014).
Figure 5: paper processed with Ninhydrin chemical to reveal latent fingerprints.
(Source: Nylon, Weising & Rotter, 2014)
2.3 Challenging the validity of fingerprint identification
Fingerprints are used by forensic experts to prove the guilt and innocence of a person and it is the most trusted form of forensic evidence in the court of law. According to the study conducted by The National Institute of Standard and Technology (NIST), fingerprint identification is one of the most reliable measures for verification as well as the identification system (Nist.gov 2018). Because of this high rate of reliability, numerous agencies responsible for law enforcement are using automated devices of fingerprint matching. Despite fingerprints unique characteristics and new tool and techniques, there are various techniques used by forensic examiners which are not scientifically tested. The validity of fingerprints evidence in effect comes down to an issue of trust and credibility.
2.4 Forensic DNA Fingerprinting
The technique used in DNA fingerprinting is the comparison of nucleotide sequences of DNA fragments collected from different sources. DNA is treated with different endonucleases and enzymes which are broken down into DNA strands. DNA fingerprinting is primarily a laboratory technique that is adapted for establishing a link between suspect of a crime and biological evidence. The method of DNA fingerprinting is primarily used in criminal investigation. In this method, a DNA sample is collected from the crime scene and is compared with a DNA sample collected from the suspect. On comparing these two DNA samples if a profile matches then it is concluded that the evidence has come from the suspect (Yourgenome.org, 2018). In contrary to this, if profile of the DNA does not match, then it is concluded that evidence has not come from the suspect. In addition to finding a suspect for criminal investigations, DNA fingerprinting is also used for evaluation of paternity (Trivedi, 2015).
2.5 DNA evidence in a criminal trial
DNA fingerprinting is widely used for determining characteristics of an individual which is also a unique factor like that of DNA. DNA fingerprinting is most commonly used as a technique of criminal forensic investigation since they involve distinctive sequence nucleotide in the form of VNTRs and STRs (Crauwels et al. 2014, p 01). Under this system DNA sample of one or more individuals are compared. A DNA sample is collected from the crime scene which has a high likelihood to be the DNA of crime convector (Buckleton, Bright & Taylor, 2016). Furthermore, another DNA sample of a suspected individual is found and matched with the DNA sample collected from the crime scene [Refer to Appendix 1]. If both the DNA sample matches then it is concluded that the suspect was present in a crime scene (Geneed.nlm.nih.gov, 2018).
Figure 6: DNA sample collected from crime scene matches with 2nd suspecter
(Source: Geneed.nlm.nih.gov, 2018)
2.6 DNA typing/fingerprinting controversy
This review is about the controversies that have occurred in DNA typing and fingerprinting. In some case, DNA fingerprinting can also be unreliable as well. In several cases, the researcher has forensic investigators face difficult type in interpreting probability of matching DNA. Studies had shown that jurors of criminal trial are seldom convinced by a matching probability of 0.1 among 100 sets of DNA strands. Furthermore, in many cases, the connector of a crime gets released without getting punishment as their DNA does not match with sample DNA collected from the crime scene. One such example can be seen in criminal case of John Schneeberger who being the convector was released as his DNA did not match at the first three attempts with the DNA collected from the Crime scene. The investigators failed to match the DNA samples as Schneeberger had surgically implanted a Penrose drain under his arm which was filed with anticoagulants containing foreign blood (Heras et al. 2015).
3. Influence of subjective thought
3.1 Contextual bias in forensic science
Contextual bias arises when the judgment passed by an individual is influenced by information that is irrelevant and inappropriate to the task. In the forensic science, it is often seen that the examiner who is examining the fingerprints receives the file containing the prints and a case summary is more likely to find out that the fingerprints match rather than an analyst who has no prior information of the case (Quigley-McBride & Wells, 2018).
In the field of forensic science, the experts examine the areas where two patterns or evidence of print are enough to conclude a match. The recent cases of fingerprint identification error have gathered attention due to its perceived liability. The benefits of contextual bias can be derived from the different school of thoughts. One of the major benefits is that examiners are not provided with any information of the case so that the task can be effectively completed without any bias. The debate on the existence of contextual bias has been prevailing since eternity. Few authors who have been researching on this issue claim that the issue of contextual bias is a real concern in forensic science. However, few experimental studies have shown that the bias does not exist in forensic science.
3.2 Contextual bias also exists in fingerprint identification
It was reported in 2004 that the FBI had arrested Oregon attorney Brandon Mayfield as the police suspected that he was involved in incident of a train bombing in Madrid (Stoel et al. 2014). He was arrested based on the fingerprints found on the bag of detonators. However, after a few days, it was found out the actual culprit was someone else and Brandon Mayfield was released. The contextual bias in the investigation and verification process led to this error.
3.3 Contextual bias in DNA fingerprinting
It was reported a few years ago that the German police had been tracking a serial killer over the decade that killed a young police officer in the country. The DNA evidence found from the murder site showed that the suspect was the same person who had committed several murders, robberies. Even though the suspect’s face was never revealed the genetic analysis identified that the suspect was a woman (Edmond et al. 2015). However, there was no fixed pattern in which she committed crimes. Sometimes she would fly away to other countries which made it even difficult for the police to track her. Surprisingly, the suspect was never arrested. It was later revealed that the DNA collected did not belong to the murderer rather it belonged to a female factory worker who had contaminated the cotton wool swabs which were used in the lab tests of the police (Searston, Tangen & Eva, 2016). Here comes the existence of contextual bias in DNA fingerprinting. The DNA fingerprints do mark out individuals as biological barcodes but labeling them to a person whose impressions were gathered from a crime scene is a totally different matter altogether.
Admissible evidence in a court of law refers to the testimonials, documentaries or tangible evidence which could be introduced to a pathfinder such as a judge or a jury member to prove a point which is put forward by a party. It has been observed that the expert evidence led by the prosecutors are often misused by the jury in such a manner which could not be easily addressed by conventional trial safeguards (Gupta et al. 2016). The risks accentuate in areas where the opinions derived from forensic methods are not formally evaluated and in those areas the admissibility mainly depends upon the legal recognition of the witness and some other formal qualifications which are relevant. The discretionary exclusions to contextual bias in forensic science include Section 135 and Section 137. Section 137 is a mandatory bannned: if arbitration cites evidence its biased effects are outweighed by the extraordinary risk to the accrued, it should be forbidden (Douglas et al. 2015, p 01). Whereas, section 135 and then again the optional refusal to admit proof of the inability to accept that it is unfounded biased, confusing or unclear, or causing unnecessary uselessness. It also has to be a great inconsistency between the "evidential tribute" and the "danger" of the motivation behind section 135.
3.5 CSI effects
The CSI effects are beliefs that are primarily held among the law enforcement personnel’s and prosecutors that the forensic science television shows have an influence on the jurors and they develop unrealistic expectations regarding forensic science during a criminal trial. The research findings of CSI effects are that the popular television dramas focus on forensic science and that affects the behavior of the jurors (Stevenage & Bennett, 2017). The perceptions of the jurors are influenced and the need for specific forensic evidence is reflected in their decisions in the courtroom. The effects of CSI are hypothesized in two ways-
The jurors start expecting more evidence that is necessary and available.
The jurors start building greater confidence in forensic and DNA evidence.
4. The influence of human error
4.1 Contamination of DNA and fingerprints specimen
In numerous cases, it is observed that specimen of DNA and fingerprints have been contaminated intentionally. A DNA specimen gets contaminated in laboratory examination or in crime scene as well. In most cases, investigators only wear latex gloves but no mask, hat and have a short-sleeved shirt. This may result in contamination of DNA specimen left by the suspect as epithelial cells nose, mouth, arms and head of investigator can be left in the crime scene (Van Embden et al 2016).
Figure 7: Potential epithelial contamination sources
(Source: Van Embden et al. 2016)
The Case of RV Button
In the case of RV Button  QCA 133, it was observed that there was no available specimen during the trail. DNA profile was established from spermatozoa however apparently, they were not able to match DNA profile of the convict. The case encountered numerous dark phases which primly occurred due to international contamination of DNA fingerprinting (Netk.net.au, 2018).
The Case of Indiana (faulty fingerprints analysis)
In this case of Lana Canen, convicted for the murder of her neighbor Helen Sailor in 2002. At trial, Expert Dennis examined that a fingerprint recovered from a plastic pill bottle found at the crime scene matched Canen (Chen, Qu and Cui 2017, p 1). This was the only evidence against her and she was convicted for 55 years in imprisonment. Later, it was found that due to the improper and faulty analysis of fingerprints Canen leads to the wrongful conviction (Strathcyde, 1997)
The failure of quality assurance and quality control included the weather conditions, the packaging, and storage which contaminated the sample and methods of lifting.
4.2 Probabilities and error rates
There are numerous cases of DNA contamination that resulted in error result and failure reports. Main cases of error results are contamination laboratory processes and human error. Some human errors can be checked whereas gross contamination in sample collected for crime scene may lead to irreversible consequences. To calculate the error rate and probability of DNA specimen contamination, the forensic statistical model such as Bayesian Network can be adopted. The following table shows some reported error rate of DNA (Vos et al. 2015).
Figure 8: Reported error rate of DNA
(Source: Vos et al. 2015)
4.3 Influence of the system
Technically the reliability of DNA evidence depends on numerous factors such as quantity and quality of analyses sample and technique and laboratory used in analyzing those samples. The reliability of DNA analysis depends on quality and quantity control practiced in the forensic laboratory. It helps in ensuring the result of each DNA analysis meets the required quality standard. It also refers to ineffective monitoring, verification, and documentation of DNA analysis laboratory performance (Alrc.gov.au, 2018).
4.4 Impact of a universal process
DNA fingerprinting has a much profound impact than fingerprinting to ensure evidence that is incontrovertible. Unlike fingerprinting, DNA fingerprinting is used for numerous things apart from finding evidence in the crime. It is also used in the diagnosis of inherited disease, personal identification and developing courses as well (Leon and Jones 2014, p 74). DNA fingerprint is often used for the diagnosis and detection of disease in children in an early manner but analyzing DNA structure form parental specimens (Lennard et al. 2016). This leads to proper treatment of the child [Refer to Appendix 3].
The aim of this critical report was to evaluate and compare the reliability of latent fingerprint and DNA fingerprint. It is observed in this report that both latent, as well as DNA fingerprints, are important for finding evidence in a crime scene but there are controversies in both the segments. In case of DNA fingerprint, contamination of evidence can occur intentionally in the crime scene, forensic laboratory and by investigators. On the other hand, contamination of latent fingerprint can occur due to improper lifting methods, ineffective storage and packaging, and weather conditions. Thus, it is recommended to incorporate further studies and improved technology to increases reliability in both the sections. Appendices
Appendix 1: Math Analogy to DNA Evidence
Appendix 2: Probabilistic Genotyping via Modelling Simulations
Appendix 3: Single-Source Sample vs Mixture Results