At Issue
6/13/2011 3:06:16 AM EST
Forensic science: friend or foe?
In this first instalment of a two-part series, Kiki Wong and Anthony Tsang discuss the impact of forensic science on the legal system and the influence of forensic television shows on jurors and lawyers.
Posted by LexisNexis

What is forensic science?

Forensic science concerns the use of a range of sciences to determine certain factual issues for the purpose of civil and criminal proceedings. The first written account of forensic science was in 12th century China. A death investigator was sent to a village where a local farmer had been murdered. First, the inspector identified the murder weapon as a sickle by striking into an animal carcass with various blades and compared the marks made by them. From that, he deduced that the murderer was most likely to have owned a sickle and demanded that all the villagers bring their sickles and display them before him. Soon, flies began to gather around the traces of blood on the weapon which was used to murder the farmer. The owner of the sickle eventually broke down and confessed to the murder. This crude method is highly unlikely to be accepted by courts today, but it is a good example to illustrate how basic science was used to logically determine an issue and deduce a chain of events.

In the early 1900s, forensic science was formally introduced to most of the Western world, including the United States, United Kingdom, Germany and other parts of Europe, for use in dealing with both civil and criminal proceedings. As technology, biology and science evolved in the 1960s and 70s, courts have routinely admitted opinion evidence based on forensic science.

Forensic services in Hong Kong

In Hong Kong, most forensic services are processed by the government laboratory’s own forensic science division. The division’s main responsibility is to provide these services to government departments such as the Hong Kong Police Force, the Hong Kong Fire Services Department and the Hong Kong Customs and Excise Department. It also deals with crime scene examinations and supplying experts in specialised fields, such as blood splatter analysis and road traffic accident reconstruction. The forensic science division is divided into two groups and these groups are subdivided into smaller sections.

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The Criminalistics and Quality Management Group carries out work in general biological, chemical and physical fields, as well as overseeing the quality of work for the forensic science division. For example: the parentage testing section deals with parent/child relationships in connection with immigration cases; the physical sciences section deals with road traffic accident reconstruction, the testing of alleged counterfeit items and the examination of tire, tool and shoe marks. The Drugs, Toxicology and Questioned Document Group carries out work in specialised areas of forensics, in particular, analysing suspected dangerous drugs and dealing with drunk driving cases. The questioned document section is one of the leading authorities on the analysis of Chinese handwriting. For further details about the work of the government laboratory see:

However, one main forensic area that is not included in the government laboratory’s work is fingerprint analysis. This is carried out by Hong Kong Police Force officers. Therefore, if a person wants to be become a fingerprint examiner in Hong Kong, not only does he/ she need to undergo training to first become a police officer (which takes at least two years) but further training in fingerprint examination which may take a further four to five years) is also required.

This differs from the United Kingdom and some states in the United States, where a person can become a fingerprint examiner from the outset by undergoing the requisite training and passing examinations to become a qualified expert within four to five years. It is the authors’ view that fingerprint analysis in Hong Kong should also be open to those who do not want to become a police officer and want a more direct career path to becoming a fingerprint examiner. Furthermore, a fingerprint examiner can perhaps better focus on the task at hand without the added pressures of other police duties.

Traditional and modern forensics

There is a diverse range of forensic fields and all of them apply sciences to decide a factual issue for the purpose of legal proceedings. They include:

• Forensic DNA – the use of a person’s unique DNA sequence to place him/her at the scene of crime, or answer questions about a paternity/maternity relationship.
• Fingerprints – the study of fingerprints and palm prints.
• Forensic toxicology – the analysis of chemicals or drugs in the body.
• Trace evidence – the study of fibres, hair, paint, glass and other contact evidence.
• Forensic pathology – the marriage between medicine and pathology to determine the cause of death or injury.
• Forensic anthropology – the study of the human skeleton.

The list above provides some of the more traditional forensic sciences that are widely accepted by the courts. Other, but less well known, fields include:
• Forensic odontology – the evaluation and examination of dental imprints.
• Forensic podiatry – the study of footprints (fingerprint examiners can also analyse footprints) and footwear at crime scenes.
• Questioned documents – the examination, study and comparison of documents to determine the authenticity of the questioned documents.
• Handwriting analysis – the examination and comparison of suspected forged handwriting and controlled sample of handwriting (including signatures).
• Ballistics – the study of firearms including the striation marks on bullets to determine which weapon fired it and where it was fired.
• Forensic psychiatry – the study of the mind in relation to crime.
• Forensic entomology – the study of insects to determine time of death or whether a body has been moved from one place to another.

Before 1930, there was no official crime laboratory anywhere in the world. The growth of forensics stemmed from its police departments’ attempts to utilise scientific methods to solve crimes. They did this by enlisting the help of university professors who collected evidence and conducted their own testing on their own premises. For the next 10 years, science professionals established laboratories and these were developed by criminal investigations in their respective regions, the largest being the Federal Bureau of Investigations (FBI) which was formed in 1932. They developed pioneering research from the US, the UK, Italy and Germany to create the most technologically advanced official crime laboratory, and it still remains so to this day. The development of forensics was a symbiotic relationship between the police, government-employed forensic scientists and the prosecution. This close-knit network has not changed much over the last 80 years.

In the last decade, many issues over forensic science have arisen between lawyers and scientists. Previously, courts have been impressed with the testimony of experts simply because of an expert’s credentials. It was assumed that because of the expert’s high qualifications, his/her claims and assumptions regarding traditional forensics have been
thoroughly tested and were factually true and accurate. However, from a scientific point of view, if the forensic field is highly subjective, just how scientific are the results and conclusions reached? This holds true for comparative fields such as handwriting, ballistics, tool marks, bite marks, tire marks and footwear marks.

A voir dire is held to effectively filter out what is commonly referred to as ‘junk science’ before the start of the actual trial. Junk science is a whole topic in itself. But, put simply, it may consist of a publication or a study that has all the trappings and elements of science seen from a layman’s perspective, but it is ultimately flawed as the results and data indicate sweeping conclusions. Thus the conclusions are not credible from a scientific point of view. Junk science includes, for example, the use of alternative healing methods, such as homeopathy (the use of alternative medicines) and Reiki (spiritual healing), astrology and health scares.

From a legal perspective, the question is whether these forensic fields and techniques are admissible even when they lack scientific validity. This very issue was raised in the landmark case of Daubert v Merrell Dow Pharmaceuticals 509 US 579 (1993) and subsequently gave rise to what is known as the ‘Daubert Standard’. Since 1993, most US states have implemented the Daubert Standard (except in Alabama, California, Illinois, Kansas, Maryland, Florida, New York, Washington, Michigan, Minnesota and Pennsylvania where a similar standard known as the ‘Frye Standard’ is used). The Daubert Standard essentially lowers the threshold for the admission of more modern but scientifically proven forensics and raises the threshold for traditional forensics, which may be lacking in scientific foundations.

The trial judge uses the Daubert Standard to ascertain whether the forensic field itself is admissible. There are five key factors that all potential forensic techniques must follow:

1. the technique has been tested in actual field conditions as opposed to limited controlled conditions in a laboratory;
2. the technique has been subjected to peer review and publication;
3. the potential or known error rate must be very close to zero;
4. standards exist for the control of the technique’s operation; and
5. the theory and/or technique is accepted by the relevant scientific community.

Questionable forensic techniques

Presently, forensic fields which have been previously accepted and appeared scientifically sound have been heavily under fire due to the Daubert Standard. These fields include:

Bullet lead analysis – this analyses the chemical composition of the lead of a bullet because it was thought to be so distinctive that it could be traced all the way back to the original batch where it came from. However, in 2005, the FBI stopped using this technique because it was discovered to be too unreliable.
Ballistics – it is common knowledge that bullets fired from a specific gun will show distinctive striation marks. It was widely accepted that if the crime scene’s striation marks of a bullet matched that of the controlled sample bullet (fired from the suspect’s gun), then it is a solid conclusion that the bullet was fired from that gun. However, research by Bruce Moran, a firearms examiner with Sacramento County, California, showed that consecutively manufactured Smith and Wesson revolvers produced the same striation marks. These identical grooves could easily give the impression to an expert that the same gun had fired the bullets when in fact they were not.

Recently, one of the most questionable forensic techniques is forensic odontology (dentistry). For example, if a killer took a bite of an apple at the crime scene before committing the murder, it could be used as evidence that connected the killer to the crime scene. There have been several landmark cases such as Ray Krone (Arizona), Calvin Washington (Texas) and Willie Jackson (Louisiana) where bite mark evidence was produced and lead to murder convictions. However, they were later released due to subsequent developments in DNA evidence which proved that they were wrongly convicted. As a result, they received substantial compensation.

A study by a member of the American Board of Forensic Odontology showed that certain dental identification techniques had error rates of above 60%: see S Lovgren, ‘CSI: science eluding reallife crime labs’ (National Geographic News, August 2008); available at: Most forensic scientists have argued that with such high error rates, the field is not scientifically reliable and the evidence should not be admissible.

Admissibility of forensic evidence and the use of expert witnesses

Generally, all types of forensic evidence should be admissible, and it is common knowledge that the judge decides whether any type of evidence is admissible. Barristers may call upon an expert witness to give evidence in support of their case. The use of expert witnesses is commonplace in courts worldwide. A judge hearing the proceedings will determine the admissibility of the proposed expert evidence. Several criteria must be met in order that their testimony may be admissible: 

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In 2005, the Law Commission for England and Wales put forward a proposal to adopt the Daubert Standard or a standard akin to it. The Commission enlisted the support of the Forensic Science Advisory Council to work with judges, scientists and other key members of the criminal justice system to build on the original Daubert Standard. This, in turn, has led to the establishment of the House of Commons Science and Technology Committee which is in charge of legal matters relating to science and technology in England and Wales. Since 2009, the Committee began drafting a guideline on setting the standards of forensic evidence use in court. A definitive guideline has yet to be determined, and it is expected that, towards the end of 2011, the Committee will be submitting a paper to the House of Commons in this regard.

In Hong Kong, the Daubert Standard (or something similar) has not been implemented. This may be because cases requiring forensic evidence are not as plentiful as in the US or the UK. However, it is submitted that, nonetheless, the Daubert Standard (or something similar) ought to be implemented because it will aid the judiciary by reducing the volume of admissible evidence, where such evidence is concerned with a field that is not scientifically reliable. If such a standard were in place, Hong Kong lawyers would have an extra tool; that is, not simply questioning the credentials of the expert but also
questioning the reliability of his/her field of expertise.

The CSI effect

With the increased popularity, in recent times, of forensic-based television series like CSI (Crime Scene Investigation), Dexter and Bones, the general public has started to appreciate the importance of forensic evidence. Such television series have led them to believe that any and all forensic findings presented by law enforcement agencies must be true and accurate. A leading American forensic scientist, Thomas Mauriello, at the Department of Criminology, Maryland, commented that about 40% of the techniques used in the CSI shows do not exist: J Wise, ‘Hollywood profiling: the impact of the CSI effect on the use of forensic science in New South Wales’ (Expert Evidence Conference, Canberra, February 2011). The shows also ignore all elements of uncertainty and present conclusions as absolute truths; but absolute truths are contested issues in forensics and rarely do they really exist.

There have been many changes in human behaviour resulting from this CSI effect right across the board from criminals to lawyers and jurors.

Criminals after watching the television shows are made aware of certain techniques used by forensic departments. This may give them a false impression that they are smarter than the police. In the US, it was found that some rape victims were forced by their assailants to shower and use bleach to destroy contact evidence on their bodies. Criminals in ransom cases avoided licking envelopes to prevent leaving traces of
DNA from their saliva. Instead, they have used adhesive tape, which, unbeknownst to them, left clear imprints of their fingerprints and sometimes hair samples. Thus, their attempts at concealing one form of evidence actually generated another form of evidence.

Since 2000, lawyers worldwide have been adjusting their trial preparations to include their own forensic experts. Opening and closing statements have been used to minimise the impact of the CSI effect. Dr Monica Robbers of Marymount, Virginia, conducted a survey in 2008 which showed that 80% of all American legal professionals felt that juries’ verdicts have been affected by forensic television shows: see MLP Robbers, ‘Blinded by science: the social construction of reality in forensic television shows and its effect on criminal jury trials’ (2008) March 19(1) Criminal Justice Policy Review 84. Some jurors felt that these shows have educated them and made them more equipped to make decisions. Some felt that if there was any DNA evidence against an accused, he/she must be guilty. Others felt they should acquit because the forensic evidence they expected was lacking. In one case, a juror even complained that the police were careless in their investigation because they did not dust an entire lawn for fingerprints. Of course that was not police protocol; it was neither practical nor possible. It was simply the juror’s misunderstanding of what is forensics and his attempt to apply what he had seen on these shows to the circumstances of the case. Clearly, a little knowledge can be very dangerous as it has profound effects.


It would appear that the US is leading the general trend in setting a minimum standard for the various forensic sciences. Hopefully, all jurisdictions, including Hong Kong, will follow suit in the near future by implementing a standard similar to the Daubert Standard. The effect of introducing such a standard is positive because it will put pressure on experts in all forensic fields. Not only will their experience and credentials be questioned, but their methodology must be flawless; it will highlight the necessity of contesting more regularly the forensic techniques used by them when providing evidence in court. For forensic scientists, a standard will also provide recognition in their field of expertise and methodology. Ultimately, and perhaps most importantly, it will save a lot of time and legal costs. 


Kiki Wong
Head of Forensics
The Forensics Company


Anthony Tsang
Head of International Relations
The Forensics Company


Kiki Wong及Anthony Tsang在其分為兩部分的首部分論述中,論及法證科學對法律制度所產生的影響,以及有關法證科學的電視節目對陪審員和律師的影響。













• 法證DNA—使用個人獨一無異的DNA序列,把其置身於案發現場,或回答有關父親/母親關係的問題
• 指模—研究指紋和掌印
• 法證毒理—分析人體內的化學物或藥物
• 痕量證據—研究纖維、頭髮、漆油、玻璃及其他接觸證據
• 法醫學—藥物與病理的結合,以決定死因或受傷原因
• 法醫人類學—研究人體骸骨以上為法庭廣為接納的較傳統法證科學,其他不大為人熟悉的範疇包括:
• 牙齒法證學—評估和檢驗牙印
• 法證腳學—研究案發現場的腳印(指紋檢驗師亦可分析腳印)及鞋印
• 文件鑑辨—檢驗、研究及比較文件,以確定文件的真偽
• 字跡分析—檢驗及比較懷疑偽冒字跡,以及對照的字跡(包括簽名)樣本
• 彈道學—研究火器,包括子彈的坑紋,以確定是哪種武器射出,以及從何處射出
• 法醫精神科—研究犯罪思維
• 法醫昆蟲學—研究昆蟲,以決定死亡時間或人體是否從一處被移到另一處




Daubert v Merrell Dow Pharmaceuticals 509 US 579 (1993)這宗具重大意義的案例中提出,其後產生了所謂的「杜伯特標準」(Daubert Standard)。

自1993年以來,大部份美國州份均推行「杜伯特標準」(除了阿拉巴馬、加州、伊利諾、堪薩斯、馬里蘭、佛羅里達、紐約、華盛頓、密歇根、明尼蘇達及賓夕法尼亞,其所使用的是類似的標準,稱為Frye Standard)。「杜伯特標準」主要是將較現代化而獲科學證明的法證之接納門檻降低,並將傳統法證的門檻提高,因為後者可能欠缺科學基礎。原審法官使用「杜伯特標準」以確定法證範疇本身是否可獲接納。主要因素共有五項,所有法證技巧必須遵從:

1. 技巧已在實際範疇情況測試,相對於受限制的實驗室情況;
2. 技巧已獲同行評審及公布;
3. 潛在或已知錯誤率必須非常接近零;
4. 已有標準控制技巧應用;以及
5. 理論及/或技術獲相關科學領域接納。受質疑的法證技巧


• 子彈鉛分析—分析的是子彈鉛的化學組成,因為具獨特性,可追溯至其原來的批次。不過,聯邦調查局在2005年停用此技巧,理由是太不可靠。• 彈道學—從特定槍械發出的子彈會有獨特的坑紋是常識。一個被廣為接納的看法是,如案發現場的子彈坑紋符合(疑犯槍械發出的)對照樣本的子彈坑紋,可靠的結論是子彈乃從該支槍械發出。不過,加州沙縣的槍械檢驗員Bruce Moran 的研究顯示,同時製造的Smith及Wesson轉輪手槍的子彈坑紋相同。這些相同的坑紋很容易讓專家推斷子彈是由同一支手槍發出,而事實並非如此。最近,最受質疑的法證技巧,是牙齒法證學。舉例說,如殺手在案發現場犯謀殺案前吃了一口蘋果,這就是殺手與案發現場的關係。數個具重大意義的案例,如Ray Krone (阿利桑那)、Calvin Washington(德薩斯)及Willie Jackson(路易斯安那州),均是提供咬痕證據,從而被裁定謀殺罪成立。不過,他們最後獲釋,因為DNA證據的其後發展,證明他們被誤判。因此,他們獲得了巨額賠償。

美國牙齒法證學委員會一名委員的研究指出,若干牙齒鑑證技巧的錯誤率高於60%:見S Lovgren, ‘CSI: science eluding real-life crime labs, (National Geographic News, 2008年8月);載於:。大部份法證科學家認為,錯誤率高達此水平,此範疇在科學上並不可靠,因此證據不應被接納。








隨著近期以法證為本的電視劇如CSI (Crime Scene Investigation), Dexter和Bones日益受到歡迎,社會大眾開始重視法證證據的重要性。這些電視劇集令他們相信,執法機關展示的所有法證結果都是真實而準確的。馬里蘭州的犯罪部門的著名美國法證科學家Thomas Mauriello表示,在CSI劇集當中約40% 的技術並不存在:J Wise, ‘Hollywood profiling: the impact of the CSI effect on the use of forensic science in New South Wales’(2011年2月,坎培拉,專家證據會議)。此劇也忽視所有不確定因素,把結論展現為絕對真確的事實,但絕對真確的事實,是法證學的具爭議性事宜,而且很罕見。

此等罪案現場勘查的影響,為人類行為帶來很多改變,影響遍及罪犯以至律師和陪審員。觀看過有關電視節目的罪犯會察覺到某些為法證部門所使用的技術,讓他們誤以為自己比警方更聰明。在美國,兇徒強迫一些強姦受害人洗澡,並使用漂白劑毀滅受害人身上的接觸證據。贖金案件的罪犯避免舔信封,以免口水留下 DNA。他們使用膠紙,但這反而留下清晰的指紋,有時甚至有頭髮樣本。他們企圖掩飾一種證據,實際上卻產生另一種證據。

自2000年起,全球的律師都開始調整他們的審訊準備工作,並將其法證專家包括在內。啟案陳詞與結案陳詞的使用,有助將罪案現場勘查的影響減至最低。2008年,維珍利亞州瑪利曼的Monica Robbers 博士進行了一項研究,顯示80%美國法律專家認為陪審團的裁決受到法證電視節目的影響:見MLP Robbers, ‘Blinded by science: the social construction of reality in forensic television shows and its effect on criminal jury trials’ (2008年3月)19(1) Criminal Justice Policy Review 84。




Kiki Wong
Head of Forensics
The Forensics Company


Anthony Tsang
Head of International Relations
The Forensics Company

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