Forensic Reconstruction – A Primer for Lawyers
What is Forensic Reconstruction?
Forensic reconstruction is the application of various forensic tools to uncover the what, who, where, when and how (four Ws and H) of a crime, traffic accident or other incident. It often applies in relatively complex cases involving multiple parties, their actions, movements and interactions, and a sequence of events.
Forensic reconstruction entails a holistic and coherent evaluation of diverse types of evidence, and how they relate to the crime, accident or incident. It is not merely a summary or structured compilation of forensic findings by other experts. Reconstruction is a non-standard, multi-faceted examination which entails both scientific actions and thought processes. It requires interpreting backwards from the scene and multiple evidence types that lend mutual support to each other. Key factors and parameters associated with the incident are often identified, and hypotheses are then formulated and tested, sometimes by simulating the physical conditions of the scene.
Reconstruction is not speculation of what could have happened. It must be based on, and supported by facts and objective information obtained from careful, reliable examination of physical evidence. Reconstruction involves scene analysis, forensic laboratory examinations, and an overarching critical analysis and synthesis of all known evidence and facts.
Value of Reconstruction
The primary purpose of forensic reconstruction is to aid the Court in understanding, from a scientific perspective, how the many different types of physical evidence relate to the crime, accident or incident.
Often, it is relatively easy to infer through physical evidence (DNA profile, trace evidence, shoeprints, toolmarks, etc) that an individual was present at a scene, and was in some way connected to the crime or incident. These examinations, however, may not answer the central question of the contribution and extent of the individual’s involvement in the crime or incident. Valuable and essential as findings from each type of physical evidence are to investigation, prosecution and defence, a consideration of each evidence type individually without forensic reconstruction may be a sub-optimal use of the evidence owing to the fragmentary, disconnected approach. Likening the better known evidence types such as DNA profiles, trace evidence and impressions to key pieces of the puzzle, forensic reconstruction brings these important pieces together by determining how the various evidence relate to one another. More importantly, it adds connecting, bridging pieces in between them to build a more complete and clearer picture, making the whole greater than the sum of its parts.
Common Types of Reconstruction
The most common types of forensic reconstruction in Singapore are related to:
1. violent crimes involving bloodshed;
4. unnatural deaths, including hanging and fatal fall from a height;
5. traffic accidents; and
6. drug trafficking.
The reconstruction of violent crimes with bloodshed usually includes the bloodstain pattern analysis of the scene and exhibits submitted to the forensic laboratory. This reconstruction uncovers the nature of the violent action, weapons used, locations, relative positions and movements of the assailant and the victim during and after the crime, number of blows, source of the bloodstains, possible mechanism of bloodstain formation, alterations to bloodstains after the crime, and possible sequence of events. In reconstructions involving bloodstain patterns, findings from the medical and autopsy reports are an important link to ensure that the injuries on the persons involved, especially their open and active bleeding wounds, are consistent with the bloodshed at the scene.
Shooting reconstruction evaluates the circumstances and physical evidence associated with the shooting scene in order to establish the most probable sequence of events related to the shooting. It may also uncover the following information: shooter identification through gunshot residues testing, positions of the shooter, victim or target, impact points, bullet trajectory, ricochet, distance of firing, type of firearm used and association of bullets and cartridge cases to firearms. Trace evidence and bloodstain patterns found at the scene and on the victim and assailant augment the reconstruction. They provide supportive evidence on the bullet trajectory, persons involved and their movement and injuries and locations when blood was shed. When the various types of evidence are combined, the reconstruction may even shed light on the possible sequence of shots.
Explosion scene reconstruction applies to gas, industrial chemical and condensed phase explosions, as well as improvised explosive devices (“IEDs”). The reconstruction would focus on the identity of the energetic or flammable substance, characteristics of the receptacle, materials and construction of the IED, cause or trigger of the explosion, damage and its effects. In the reconstruction of industrial gas explosions, and chemical fires and explosions, an understanding of chemical reactivity, chain reactions, spontaneous reactions, environmental conditions, industrial processes, storage and manufacturing conditions, and the tools and equipment used in the industrial process and for maintenance and repair may be required.
The reconstruction of suspicious hangings and fatal falls from a height involves developing representative scenarios and hypotheses which are often tested by simulating the physical conditions leading to the death. In the process, the reconstructionist uncovers cause-and-effect relationships to ascertain whether a suggested outcome is physically possible, given the scene, anthropometric characteristics and a specific set of conditions. The design of the simulation requires a prior determination of key parameters or factors associated with the incident and the initial state of the scene.
Traffic crash reconstruction is the application of scientific knowledge and methods to determine what happened in a traffic collision. Crash refers to rollover or collision between a vehicle and other vehicle(s), objects (road guard-rails, trees, lamp-posts, etc) or pedestrian(s). The traffic crash reconstructionist typically evaluates vehicle characteristics, damage, broken debris, trace evidence, bloodstains, final rest positions, road geometry, traffic control devices, roadway marks, video evidence and human factors. These serve to determine vehicle speed, paths, direction of force, point of impact, actions and evasive manoeuvres by the road user, right of way, blind zones, time to collision, and whether the collision was avoidable.
Drug trafficking reconstruction is carried out in cases involving multiple drug packages, various locations and several individuals operating as a syndicate. It is useful to determine each individual’s involvement and role, what occurred at each location, the manner in which drug packages were packed and concealed, transfers between locations, and the modus operandi. Relevant physical evidence includes drug contents, receptacles concealing the drugs, packaging materials, DNA profiles, and other trace evidence.
Table 1 lists some of the reconstructions and simulations employed in our local cases, and illustrates their value to investigations.
Table 1: Common Types of Reconstruction and Simulation in Singapore
Type of Reconstruction
Examples of Singapore Cases
Violent crimes involving bloodshed
“Yishun Triple murders”- PP v Wang Zhijian .
Value: Determined the sequence of events, weapons used, movement of assailant and three deceased persons and one victim, and what occurred at various locations. Movement and action of the assailant after the bloodshed.
Court trial: Reconstruction findings were useful in establishing the assailant’s involvement in the death of the deceased who fell from the flat to the ground.
Others: PP v Periyasamy Devarajan  , PP v Wang Wenfeng , PP v Daniel Vijay s/o Katherasan and others , CI into the death of David Hartanto Widjaja 
“One-eye dragon” - PP v Tan Chor Jin .
Value: Determined the movements of the gunman and the victim, their relative positions, and the sequence of firing of the six shots.
Court trial: Reconstruction findings were useful in establishing that the six shots were not fired in succession due to misfiring, as claimed by the gunman.
Others: PP v Khor Kok Soon 
Fires and Explosions
Coroner’s inquiries: Bukit Merah LPG gas explosion , CNG bus explosion , Superbowl underground gas mains explosion , Chevron Oronite chemical explosion , Kreuz Shipyard fire and explosion .
Value: Determined the nature of the explosion, type of chemicals and their reactions, and how the fire and explosion occurred.
Coroner’s inquiry: Death of Shane Truman Todd 
Value: Simulation experiments to determine whether it was physically possible for the deceased to hang himself, using the materials found at the scene.
Court trial: Experiment findings were useful in shedding light on the objects and damage marks found at the scene, and the manner and mechanics of the hanging process.
Others: CI into the death of Daryl Thong Han Jie
“Fall from a height of Sindee Neo” - PP v Chee Cheong Hin Constance ,
Value: Simulation experiments to determine the distances from the building a 25-kg child would fall based on the pushing effort (light, medium, or strong push) by a woman of Constance’s weight and height.
Court trial: Experiment results demonstrated that Sindee was not merely tipped over the railing but that she had been projected over with a force greater than that which commensurated with merely tipping her body over the railing.
Others: PP v Barokah ; PP v Tharema Vejayan s/o Govindasamy .
COI: Little India Riot - bus accident resulting in the death of an Indian national 
Value: Analysis of CCTV footage to determine the trajectory and speed of the bus, movement of the deceased, human and vehicular traffic, cognitive workload and blind zones of the bus driver.
Others: PP v Teo Tiong Kiat , PP v Han Choo Bok , CI into the death of a child 
In the early 2000s, while in the Health Sciences Authority, the forensic scientists in The Forensic Experts Group developed bloodstain pattern analysis and forensic reconstruction for application to casework in Singapore. The initial cases underwent a baptism of fire in the Courts, encountering opposing experts, and scrutiny of its validity and the scientist’s expertise. Over the last 10 years, reconstruction has proven its value and gained acceptance, although it is still subject to stiff challenges due to its significant findings of associations between the scene and the persons involved. Today, reconstruction is commonly employed in major and high profile local cases.
What the Reconstruction Process Entails
The reconstruction process entails the following:
1. Scene analysis and hypotheses formulation;
2. Laboratory examination of exhibits and reporting of findings;
3. Review of other expert reports and summary of their key findings;
4. Design and conduct of control experiments to determine mechanisms, causes and effects, and test scenarios;
5. Evaluation and inference of the available information;
6. Determination of sequences; and
7. Combining all the findings (in response to the four Ws and H) into a single, coherent narrative.
For scene examination and analysis, a visit of the fresh scene should ideally be undertaken by the reconstructionist to perform first-hand assessment of the entire scene. Appraising the original scene enhances understanding of spatial relationships of evidence, and generates useful questions for further inquiry. Scene analysis often results in a stand-alone Scene Analysis Report.
An alternative approach to visiting a fresh scene is to examine photographs, notes and measurements taken by others, either to perform or review a reconstruction. Although this perspective through proxy eyes may suffer from selective filtering of data and gaps in information, it can still uncover crucial information and flag significant issues. The reconstruction can provide insights that clarify the circumstances and details of the crime, accident or incident. An independent objective review of a reconstruction can confirm findings, bring to light new findings, or uncover errors in observation, analysis, reasoning or interpretation.
Forensic reconstruction usually culminates in Court testimonies where findings are examined and cross-examined. Alternative scenarios may be put forward, and specific aspects or findings challenged. The reconstructionist must be prepared to provide an on-the-spot opinion on the plausibility of an alternative scenario, especially when new information is provided during the Court trial.
The Reconstruction Report
The reconstruction report presents in a systematic and logical manner, not only the key findings of various forensic experts, but also the reconstructionist’s observations and analysis of the scene (physical context) and scientific reasoning, upon which inferences, interpretation and opinions are made on the crime, accident or incident. Forensic reconstruction can identify additional forensic examinations required to obtain “complete” knowledge of the case.
The reconstruction report invariably contains a qualifier indicating possible gaps in information, possible variations in the sequence of events, and limitations. Diagrams, sketch plans and annotated photographs are often included for easier understanding. Key information are often summarised in tables to facilitate digestion of information. Background data and assumptions must also be clearly stated. The reader should be able to easily distinguish facts from opinions. All reconstruction reports must be thoroughly reviewed by a second competent peer before they are issued.
For the purpose of transparency, the reconstruction report is usually detailed, and often inevitably lengthy. Justice and a person’s liberty, life and reputation are at stake; hence, it is only reasonable that the basis of the reconstruction be laid open for examination and cross-examination.
Pitfalls and Limitations
The major pitfalls and challenges in reconstruction include:
1. Oversimplification of issues – Simplification occurs when a reconstructionist neglects complexity in a scene, fails to consider all available evidence, facts and factors, or cuts corners instead of applying rigorous scientific methods.
2. Maintaining relevance and realism in simulations and scenarios – Understanding the context, establishing the key parameters, and formulating clear and relevant hypotheses are essential to the appropriate design of simulation experiments.
3. Missing out on a crucial detail which could radically alter the complexion of the matter under investigation – Forensic analysis at the scene and in the laboratory calls for a balance between speed and thoroughness, while achieving reliability of findings. An eye for relevant detail, a questioning mind, critical thinking, recognition of the incongruous, and experience enable a seasoned reconstructionist to zero in on the key issues of a complex “chaotic” scene.
4. Safeguarding against confirmation bias – Tunnel vision, expectancy effects and observer effects can taint an expert’s perception and judgment . Personal good practices, peer reviews, or scrutiny in Court are effective counter-measures against forensic bias.
5. Limitations in human factors – Human models in simulation experiments and expected rational behaviour may not adequately mirror actual human response in the heightened emotions, intensity and extremes of a crime.
Expertise and Skills Required to Produce a Reliable Reconstruction Report
A reconstructionist should not only be an expert in forensic laboratory examinations, but also be highly adept at analysing the scene, framing questions, identifying evidence at the scene, and evaluating the overall physical context. The pre-requisites and foundations of reconstruction expertise are mastery of the numerous forensic methods, practitioner knowledge in multiple forensic disciplines, and understanding of the application, strengths and limitations of the other types of physical evidence. Reconstruction requires a blend of both hard and soft skills.
Hard skills refer primarily to the proper application of scientific principles, laboratory and field instruments and analytical techniques to generate reliable and accurate measurements, identifications and comparisons.
Soft skills refer to the critical thinking skills used in problem framing and hypothesis formulation, choice of methods, design of experiments, critical analysis and synthesis of data, professional judgment, and written and oral communication of findings.
These essential skills are acquired and honed from relevant scientific education, on-the-job and specialised forensic training, mentoring and coaching, examination and reporting of actual casework, Court testimony, forensic research, presentations and publications.
Experience matters to a great extent in forensic reconstruction. It is tied to the expert’s broad and profound understanding of physical evidence, scenarios and interpretation. This comes from personal exposure to a wide range of challenging forensic problems, coupled with developing valid solutions and responses to these challenges.
There is no short-cut or hot-housing solution to develop a reconstruction expert. Simulation software, 360o scanning cameras and other advanced technological aids cannot substitute for expertise that resides only in a human being. There will be significant and obvious differences in the approach and outcome when reconstruction is attempted by a novice compared to one performed by an experienced qualified reconstructionist, owing to the depth and breadth of scientific expertise the latter possesses to scope the work, taking into consideration the various aspects of the case.
The credibility of the reconstructionist hinges not only on scientific expertise, but also on objectivity and neutrality in his/her report and Court testimony. The reconstructionist must be open-minded and non-partisan, letting the evidence speak for itself. He/she must guard against external influence and confirmation bias, and avoid jumping to conclusions without a fair and thorough examination of all evidence. A reconstruction report that is balanced, ethical and robust will include both inculpatory and exculpatory findings.
Forensic reconstruction is an essential forensic tool for the administration of justice. It is useful in cases involving shooting, violent crimes, unnatural deaths, traffic accidents, explosions and drug trafficking. Forensic reconstruction is not gratuitous speculation – every reconstruction finding and conclusion must be supported by evidence and sound reasoning. Reconstruction has three major components: scene analysis, laboratory examination of physical evidence, and an overall assessment and synthesis of all available evidence to form a coherent inter-connected whole. To be effective, the reconstruction expert needs to be experienced and highly proficient in all three areas of work. The reconstructionist integrates various expert findings, incorporates his/her professional insights and opinions into the what, who, where, when and how of a crime, traffic accident or other incident, and sheds light on the contribution and extent of an individual’s involvement.
This scientific multi-faceted forensic discipline brings out synergistic value by putting the various evidence into their physical context, and crystallising their overall significance. This augments the value of the evidence, and can help the Court reach an informed decision on the case.
What is the science behind a forensic discipline? What does the examination process entail and what are the limitations? Look out for the next article in the Forensic Science Series, presented to you by The Forensic Experts Group. It will focus on “Trace Evidence”, a forensic discipline that relates to the examination of small, often microscopic amounts of material not readily visible to the naked eye, but often left behind at the scene or brought away by the assailant. It looks into the value of identifying the trace material, establishing the associations between persons, objects and places using this evidence, and evaluating the significance of these associations.
► 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 (former leading forensic scientists in a government forensic laboratory in Singapore), who are combining more than 70 years of specialised knowledge, unique experience and skillsets to deliver high quality forensic services both locally and overseas.
1 PP v Wang Zhijian  SGHC 238;  SGCA 58.
2 “Indian national gets 16 years’ jail and caning for bashing man to death with concrete slabs”, The Straits Times *(8 April 2015).
3 PP v Wang Wenfeng  SGHC 208;  SGCA 47.
4 PP v Daniel Vijay s/o Katherasan and others  SGHC 120;  SGCA 33.
5 “Scene reconstruction: David Widjaja’s last moments”, The Online Citizen (27 May 2009).
6 PP v Tan Chor Jin  SGHC 77;  4 SLR 306;  SGCA 32.
7 PP v Khor Kok Soon  SGHC 125;  SGCA 51.
8 “Gas explosion victim dies”, Today (6 Aug 2007).
9 “NSFs escape death by 15 minutes”, The New Paper (26 Nov 2012 ).
10 Forensic investigation of an underground gas main explosion (2004), Lim Chin Chin, Michael Tay Ming Kiong, Chia Poh Ling, 56th Annual Meeting of the American Academy of Forensic Sciences, USA, Proceedings Vol 10, Abstract No. C44
11 “Accident Kills Oronite Worker”, Lube Report Vol 5 (10) (9 Mar 2005).
12 “Shipyard charged with lapses after accidents kill 3 and injure 4”, Stomp (21 Jan 2010).
13 Coroner’s Inquiry No. 2014/2012
14 PP v Chee Cheong Hin Constance  SGHC 9
15 PP v Barokah  SGHC 22;  SGHC 46
16 PP v Tharema Vejayan s/o Govindasamy  SGHC 144
17 Report of the COI into the Little India Riot on 8 December 2013 Annexes
18 “4-week jail sentence for GP who caused cyclist’s death in hit-and-run”, AsiaOne (25 May 2012).
19 “Freak accident on AYE: Cabby jailed 10 months”, Straits Times (9 Apr 2013).
20 “Boy, 2, dies after being hit by mum’s car.”, AsiaOne (15 June 2011).
21 Kassin S M, Dror I E, Kukucka J., “The forensic confirmation bias: Problems, perspectives and proposed solutions” (2013) J of Appl Research in Memory & Cognition 2, 42-52