Damage and Marks 
A Primer for Lawyers

What is Damage and Marks Evidence?

Damage and marks evidence is commonly encountered in civil and criminal cases involving product liability, vandalism, break-ins, drug trafficking, firearms, suicide and homicide. This extremely diverse evidence type consists of many forensic sub-disciplines:

1. Damage evidence comprises examinations of damage on materials which are caused by chemicals, corrosion (oxidation), heat, microbial action, mechanical forces, radiation, weathering and ageing. Damage examinations reveal possible causes, mechanisms and forces acting on the material as well as involvement of a tool, human or natural action. In this paper, we will focus on damage caused by mechanical forces, a sub-discipline which is commonly encountered in both civil and criminal cases. 

2. Marks evidence encompasses the examinations of toolmarks, firearms, manufacturing marks, footwear prints and footprints. These examinations can associate the mark or print to the item that made it, or to other marks or prints made serially by the same item. Marks evidence is closely linked to damage created by contact and mechanical forces. For example, the action of a tool on the substrate creates a damage which has characteristic marks (toolmarks). The damage caused by wear and tear on the sole of footwear imparts individuality to the footwear print.  

Basis of Damage and Marks Evidence

Forensic damage and marks examination is an applied science using validated theories from physical and engineering sciences. It is based on the comparison of class characteristics of the damage, questioned mark or print, and the suspect item, followed by comparison of their individual characteristics, if present. These characteristics often occur as indentations, striations, broken fragments, score marks, deformed material, and cuts and tears. 

The reproducibility of such evidence facilitates the comparison of test marks with the questioned ones. The conclusion of the examination depends on the quality and quantity of the class and individual characteristics.

Class Characteristics and Individual Characteristics

• Class characteristics are general features shared by two or more objects. They are often based on design factors predetermined by the manufacturer. Such characteristics alone are insufficient to define the individual item, but are useful for screening during the first stage of comparison. They can also quickly eliminate the source of the damage, mark or print.

• Individual characteristics are singular characteristics that establish the uniqueness of an object. These random marks and accidental imperfections are made by manufacturing processes, to which are superimposed additional, unintended individual characteristics resulting from use, abuse and environmental effects. Individual characteristics allows an item to be traced back to its particular source or origin.

Table 1: Class and individual characteristics commonly encountered

C and I represent Class and Individual characteristics respectively

How are Damage and Marks Examined?

General Laboratory Procedure

The questioned damage or mark is usually compared with test marks made using the suspect firearm, tool or object. Test prints or impressions are made using the suspect shoe, foot or tyre on a suitable substrate or surface. 

The making of test marks, prints or impressions takes into consideration the following:

1. Type of substrate bearing the mark, 

2. Manner in which the suspect item acted on the substrate, 

3. Operating surface of the suspect item, 

4. Force applied,

5. Direction in which the suspect item moved, and its angle or orientation relative to the substrate.

Class characteristics are often evaluated by macroscopic examinations with the unaided eye or at low magnifications, and may involve both qualitative assessment and measurements. Individual characteristics are often microscopic in nature, and usually require examinations at high magnifications of up to 120x. 

Range of Conclusions and Criteria

Conclusions commonly obtained are: identification, elimination, inconclusive, and unsuitable for comparison. However, intermediate levels of conclusion are possible, using modifiers such as: likely, very likely, unlikely and very unlikely. See Figure 1. These intermediate levels are often used for damage evidence, due to the lack of individual characteristics.

Figure 1: Conclusion levels for damage & marks

Identification (that the item made the mark or print) results from correspondence and concordance of all discernible class and individual characteristics. It implies that the likelihood that another object made the mark is so remote as to be considered a practical impossibility. 

Elimination of an object as having made a mark or print results from significant disagreement of discernible class characteristics and/or individual characteristics. 

Inconclusive findings may result from distortion, deformation or obliteration of microscopic detail in the toolmark. It can also be due to damage, extensive use, abuse, or re-machining (sharpening) of the tool between the times the questioned and test marks were made. Besides these limitations, a comparison may be inconclusive under the following circumstances:

1. Some agreement of individual characteristics, but insufficient for identification.

2. Neither agreement nor disagreement of individual characteristics due to an absence or insufficiency, or lack of reproducibility.

3. Disagreement of individual characteristics, but insufficient for elimination.

A mark or print may be unsuitable for microscopic examination due to obliteration or further damage.

What Does Damage and Marks Evidence Reveal?

Damage and marks evidence can reveal what happened, and how an event transpired. Such evidence is frequently associated with trace evidence. Cases involving damage evidence may require characterisation of properties of materials and the item, and simulation experiments replicating conditions to produce the damage. 

Damage analysis is an integral part of vehicular and boat collision reconstructions.¹ Skid marks enable calculation of the speed of the vehicle (prior to the skidding). Damage analysis is also useful in cases involving fire and explosions,² break-ins, wear and tear,^3,4 tampering,⁵ and faulty devices and components. 

1. Examination of a glass door hinge provided evidence that the glass shattered due to the faulty hinge separating from the wall. Such evidence is useful for product liability claims. 

2. Suspicious fracture damage of several pneumatic tubings in a pharmaceutical manufacturing plant were found to be caused by sudden overpressure, rather than human action.⁴ 

3. The damage observed on the elbow and spigot joint of a charged underground gas mains revealed a PUB town gas leak as the cause of multiple gas explosions at a restaurant located on reclaimed land at Marina South.²

4. Two cartons strapped with security seals containing luxury watches were found to be empty when the cartons were opened. Forensic examinations revealed that the security seals were intact, but heat-seal joints on the plastic straps had been tampered with.⁵

Obliterated Serial Numbers on Valuable Items 

The chassis number of vehicles and serial numbers of firearms or other valuable items are commonly obliterated and re-stamped to prevent tracing of the stolen item. Various physical and chemical techniques can however restore and reveal the original numbers.   

Damage on Clothing

Violent crimes in Singapore are often committed with knives. These weapons can result in stab-cuts, slash-cuts, chop-cuts and other types of damage on clothing. Class characteristics of knives include shape, dimensions and sharpness of the blade. Comparisons of damage on clothing with test cuts made using a suspect knife on control fabrics reveal the cutting mechanism, and whether a knife was capable of causing the questioned damage. Other common causes of damage include tearing, snagging, abrasion, and wear and tear.

1. In the stabbing of taxi driver Yuen Swee Hong by Wang Wenfeng, the deceased’s body was too badly decomposed to determine the number of stab wounds inflicted. Forensic examination of his shirt revealed 5 small cuts on the chest region consistent with stab-cuts by a knife with a pointed tip.⁶

2. The holes and fused fabric on the clothing and shoes of a young footballer who collapsed and died suddenly during training at the Jalan Besar Stadium showed evidence of intense localised heating due to the passage of extremely high voltage currents, consistent with a lightning strike.⁷

Damages on Cords and Straps

Characterisation of damage and alterations on cords and straps, aided by an understanding of their physical properties can reveal their cause and the mechanism involved. Factoring in the physical context and conditions, the scientist can provide information of what likely transpired in an incident. 

1. Forensic investigation of the sudden snapping of a reverse bungy cord during operation revealed damages consistent with failure and fracture of the bundle of rubber strands in the cord weakened by ageing, tension (stretching) and fatigue.⁸

2. In Shane Todd’s suspicious death by hanging, experiments on the stretching and relaxation characteristics of the strap which was around the deceased’s neck provided answers for the contentious issues raised during the coroner’s inquiry.⁹

Many crimes are committed where telltale footwear or barefoot prints and impressions are left behind at the scene as the perpetrator moves around the location. In cases of break-ins and vandalism, prying and cutting tools are used to force entry into premises, break open safes or vandalise property. Common packaging material such as plastic bags and films, adhesive tapes, newspapers and cartons are frequently employed to conceal weapons, wrap and transport body parts, contain drugs and stolen goods etc.   

Figure 2: Sub-disciplines of marks

Toolmarks

Perpetrators sometimes use tools in a manner different from their intended purpose, eg use a screw-driver for prying instead of tightening a screw. Since a tool is generally harder than the object it works on, the tool often leaves behind toolmarks on the metal, plastic or painted surface, which in turn transfers trace evidence such as metal particles and paint smears to the tool. The synergistic evidential value of trace and marks evidence enhances the overall significance of the physical evidence, and strengthens the conclusion. 

• In vandalism cases, forensic scientists provide insights on the directionality of the marks, likely tools used and the manner the damage was made.

Firearms 

The identification of a bullet or cartridge case as having been fired by a particular firearm is made possible by microscopic striations and indentations formed on these ammunition components by the hard interior surfaces of the firearm. When a firearm is discharged, forceful impacts and abrasion with the components of the firearm, as well as the firing and extracting mechanisms, create unique microscopic marks on the cartridge case, and striations on the bullet. 

1. Tan Chor Jin, nicknamed the One-Eyed Dragon, was found to have discharged six bullets from a pistol that was subsequently thrown into a canal, after the killing of night club owner Lim Hock Soon.¹⁰

2. Forensic examinations showed that during the 1984 Shenton Way shoot-out, it was not Khor Kok Soon’s firearm that killed the hostage lorry driver, Ong King Hock.¹¹

Footwear and Barefoot Prints

When footwear or a bare foot comes into contact with a surface, a print or impression may be left on that surface. 2D prints are made on a hard, flat surface by addition or removal of dust, blood or other materials. 3D impressions are made on soil and carpet. Optical and physical techniques or chemical enhancements assist in revealing details in the print or impression.

For shoeprint comparison, the forensic scientist first identifies the sole pattern and class characteristics. Shape and dimensions of the sole outline and various elements (eg arrangements of blocks of various geometric shapes, the company logo), including their spatial arrangement, can narrow down the shoe print to a specific sole pattern. The wear pattern, foreign objects adhering to the sole, and other damage on the sole, such as scratches, nicks, cuts, and gouges form the individual characteristics. The questioned print or impression is conclusively associated with a suspected footwear when the individual characteristics are in sufficient agreement with those of the test prints or impressions made by the suspected footwear. 

1. Dusty shoeprints on a sheet of A4 paper found on the cargo bed of the truck used to transport over $1.3 million dollars worth of handphones were made by a sandal worn by one of the three assailants involved in the robbery and killing of the driver Wan Cheon Kem.¹²

2. Comparison of impressions shown in photographs of the deceased’s forehead with the shoes recovered from the three accused persons and the deceased indicated that an impression on the deceased’s left forehead was similar to the outsole pattern of the first accused’s track shoes.¹³ 

3. Bloody footprints at the scene provided vital evidence on the relative movements of the three deceased persons, the severely injured victim and the accused Wang Zhijian.¹⁴

Manufacturing Marks

Manufacturing marks are found on mass-produced products such as plastic bags, adhesive tapes, newspapers and even gold ingots. They result from irregularities and minute defects on machinery parts, dies, moulds and tools used to form and finish the product. 

The comparison of manufacturing marks can determine whether an item originated from the same batch or was made sequentially by the same machine in the manufacturing plant. Manufacturing marks include heat-seal marks, striations on plastic bags, indentations on drug blister packs, and defects on printed material. 

We successfully applied manufacturing marks comparison to plastic medicine bottles¹⁵ in 2004; to packaging materials related to drug offences¹⁶ in 2009, and more recently to counterfeit drugs¹⁷ and medical devices.¹⁸ This technique was pivotal in ascertaining the counterfeiting of a renowned brand of contact lenses and its packaging, resulting in the recall of the product from the local market. 

• In the Huang Na case, vegetable packer Took Leng How tightly wrapped the eight-year-old girl in nine layers of plastic bags which were linked to a plastic bag found in the accused’s workplace. Not only did the free end of a partially used roll of adhesive tape found in the warehouse where Took worked physically fit the last end of the tape used to secure the carton, it also had Took’s fingerprint on the adhesive surface.¹⁹

Physical Fitting

The physical fitting of torn or cut newspapers with suspected complementary pieces or edges indicates that they were originally a single sheet. Fracture of materials such as metal, hard plastic and ceramic, and tearing of adhesive tapes and softer plastics likewise create irregular complementary edges. The physical fitting of these edges is evidence that these items were once a single object. Examples are chipped knife blades, broken vehicle lamp housings, broken glass vase, and torn or cut adhesive tapes and cordages. 

• In the Liu Hong Mei body parts case, physical fitting conclusively associated small metal fragments found among the body parts to a chopper with a broken cutting edge found in the flat of Leong Siew Chor.²⁰

Conclusion

Damage and marks evidence is often encountered in civil and criminal cases involving product liability, vandalism, break-ins, drug trafficking, firearms, suicide and homicide. Forensic examination and comparison of damage, marks and prints can reveal what happened, how an event transpired, possible causes, mechanisms and forces involved, human intervention and interactions or the use of a suspect tool. They facilitate the association of a suspect to an incident or crime, including the actions and movement of an individual at the scene, tools and objects he used and the manner they were used. Interestingly, the same forces that create damage and marks often concomitantly cause the transfer of trace evidence²¹ between the substrate and the item causing the damage, augmenting the overall evidential value of both types of evidence. 

The comparison of manufacturing marks on mass produced products enables the forensic scientist to ascertain whether two or more items originated from the same batch, or were made sequentially by the same machine in the manufacturing plant. Such evidence is commonly encountered in packaging material in drug offences, counterfeit products and homicides where newspapers or plastic bags could be used to conceal a weapon or a body. 

This article underscores, as in our other primers on trace evidence, questioned documents and forensic reconstruction, the importance of recognising and fully harnessing forensic science to seek the truth.

What’s Next?

A distinct and important area of marks and prints not covered in this present article is that of bloodstain patterns, which are commonly encountered in violent crimes with bloodshed events. Look out for the next article “Bloodstain Pattern Analysis” (“BPA”) in the Forensic Science Series by The Forensic Experts Group. It will feature the science behind BPA, common types of bloodstain pattern, mechanisms of formation, interpretation and challenges, and local case studies.  

► The Forensic Experts Group
    E-mail: [email protected]

The Forensic Experts Group (“TFEG”) is Singapore’s first one-stop private and independent provider of forensic consultancy, analysis, research, training and education for legal and law enforcement agencies, forensic and tertiary institutions, and private organisations. It comprises a team of accomplished forensic scientists, who are combining more than 70 years of specialised knowledge, unique experience and skillsets to deliver high quality forensic services both locally and overseas. While heading the Criminalistics Laboratory (Forensic Chemistry & Physics Laboratory) at the Health Sciences Authority from the mid-1990s till 2013, TFEG’s senior consultants developed forensic examinations of damage on clothing, and new sub-disciplines such as manufacturing marks, newspapers and plastic bags. They successfully applied this expertise to many local cases.

www.forensicexperts.com.sg 

References

1 “Value of paint transfer and damage examinations in the forensic investigation of boat collisions” (2009) Michael Tay, Lim Chin Chin, Lim Thiam Bon, Vicky Chow, Kee Koh Kheng, 5th European Academy of Forensic Science Conference (“EAFS”) Conference, Glasgow, UK.

2 “Forensic investigation of an underground gas main explosion” (2004) Lim Chin Chin, Michael Tay, Chia Poh Ling, 56th Annual Meeting of the American Academy of Forensic Sciences (“AAFS”), USA, Proceedings Vol 10, Abstract No. C44.

3 Causes of damages to leather products” (2002) Lim Chin Chin, Michael Tay, International Association of Forensic Sciences (“IAFS”) 16th Triennial Meeting, Montpellier, France.

4 “Damages on flexible compressed air tubings in a pharmaceutical plant” (2005) Wong Soon Meng, Lim Chin Chin, Michael Tay, IAFS 17th Triennial Meeting, Hong Kong. 

5 “Characteristics of tampered joints in plastic strapping” (2005) Su Wanjing, Michael Tay, IAFS 17th Triennial Meeting, Hong Kong. 

6 PP v Wang Wenfeng [2014] SGHC 23; Wang Wenfeng v Public Prosecutor [2012] SGCA 47.

7 “Damages to the shoes and clothings of a lightning strike victim” (2005) Kuah Kim Lian, Michael Tay, 2nd International Forensic Science Symposium, Taiwan. 

8 Causes of failure of a bungy cord (2007) Michael Tay, Lim Chin Chin, Su Wanjing, Wong Soon Meng, Chia Poh Ling, AAFS 59th Annual Meeting, San Antonio USA. 

9 Coroner’s Inquiry No. 2014/2012 into the death of Shane Truman Todd. State Coroner’s findings; accessible at:

10 PP v Tan Chor Jin [2007] SGHC 77; Tan Chor Jin v Public Prosecutor [2008] 4 SLR 306; [2008] SGCA 32.

11 PP v Khor Kok Soon [2005] SGHC 125; Khor Kok Soon v Public Prosecutor [2005] SGCA 51.

12 PP v Daniel Vijay s/o Katherasan and Others [2008] SGHC 120; and Daniel Vijay s/o Katherasan and others v PP [2010] SGCA 33.

13 PP v Kamal Bin Kupli and Others [2007] 3 SLR 649; [2007] SGHC 98.

14 PP v Wang Zhijian [2012] SGHC 238; [2014] SGCA 58.

15 “Comparison of manufacturing marks on moulded plastic medicine bottles” (2005) Vicky Chow, Lim Chin Chin, Michael Tay, 17th IAFS Triennial Meeting, Hong Kong. 

16 “Forensic analysis and comparison of plastic drinking straws” (2012) Vicky Chow, Alaric Koh, Oh Suat Ping, Lim Shing Min, Yew Sok Yee, Lim Chin Chin, 6^th EAFS conference.

17 “Detection of Counterfeit Drugs – Singapore’s Approach” (2011) Lim Chin Chin, Yong Yuk Lin, Yang Chiew Yung, APEC Life Science Innovation Forum First Anti-counterfeiting Health Products Seminar, Beijing, China. 

18 Counterfeit contact lenses; available at: .

19 PP v Took Leng How [2005] 4 SLR 472; [2005] SGHC 154; and Took Leng How v PP [2006] 2 SLR 70; [2006] SGCA 3. See also “A mango bait, a missing girl and a murder” (2007), Lim Chin Chin , Chia Poh Ling, Vicky Chow, Kee Koh Kheng, Kuah Kim Lian, Kuan Soo Yan, Lim Thiam Bon, Michael Tay, AAFS 59th Annual Meeting, USA, abstract no. B81. 

20 PP v Leong Siew Chor [2006] 3 SLR 290; [2006] SGHC 81; and Leong Siew Chor v PP [2006] SGCA 38.

21 The Forensic Experts Group, “Trace Evidence – A primer for lawyers”, Singapore Law Gazette (2015, July issue).