Steps in the forensic engineering investigative process with an Appendix on costs


Counsel benefits when they have some knowledge of the forensic engineering investigative process that is followed by a professional engineer.  The process determines why a structure failed or did not perform properly, or why an accident happened, including environment accidents and spills.

The forensic engineering investigative process results in a thorough investigation leading to an objective opinion rendered with considerable certainty.

This item identifies and describes typical steps in the forensic engineering investigative process. 

Forensic engineering investigations can be complex and time consuming involving all the steps in the process with some quite lengthy.  Or simple and quick, particularly when some steps are not needed because of the nature of the failure or accident. 

The process is followed regardless whether the professional engineer is retained by the plaintiff or the defendant, and whether retained as a consulting expert or a testifying expert.

The forensic engineering investigative process is also followed in spite of the fact that the great majority of disputes that arise from an engineering failure or an accident are settled out of court.

The word “forensic” from the Latin forum indicates that the investigative findings assist the justice system resolve a dispute – that’s certainly the case if the thoroughness of a forensic investigation keeps a dispute out of court.

A structure is anything in the built environment, including alterations of the natural environment like highway embankments and earth and rock slopes.  A failure can involve total collapse of a structure or its inadequate performance.

There are three fundamental components to the forensic engineering investigative process:

  1. Acquisition of data
  2. Analysis of data
  3. Presentation of conclusions and opinions

At some point we are interested in establishing a before/after scenario:

  1. What were the conditions existing before the failure or accident?
  2. What took place during the incident?
  3. What are the conditions existing afterwards – the property damage, the injuries?
  4. What caused the incident?

Rigid formulae for investigating failures and accidents do not exist.  But all forensic engineering investigations contain the following steps to a greater or lesser degree.

  1. Document Review
  2. Visual Assessment
  3. Field Investigations
  4. Laboratory Investigations
  5. Research
  6. Follow-up Investigations
  7. Data Analysis and Formulation of Opinion
  8. Repair and Remediation
  9. Report

Visual assessment can be broken down further:

  1. Visit and visually assess the site
  2. Photograph and videotape site
  3. Interview witnesses

Field investigations can also be broken down further:

  1. Describe the failure or accident
  2. Survey and document the damage to the structure
  3. Determine how the structure was built
  4. Determine the site conditions

Research can be broken down too:

  1. Desk studies and leg work
  2. Identify building codes and industry guidelines
  3. Identify standard of care

Most of the investigation involves gathering data and most of the report – more than 3/4, involves analysing and presenting the data.  This points to the importance of the data gathering.  The degree of certainty in the final opinion of the cause of the failure or accident is often a function of the amount of data gathered.

In fact, guidelines on failure investigation and forensic engineering issued by national engineering associations encourage professional engineers to take only those cases where they can carry out a thorough investigation and gather enough data to be able to give a reliable opinion.

Following is a brief description of each step in the investigative process:

1. Document Review

Review documents

Reviewing documents provided by counsel during the initial briefing is an important first step in a forensic engineering investigation.  These documents sometimes provide the only data available to an engineer investigating a failure or accident.  Documents include material like the following:

  1. Client narrative
  2. Discovery transcripts
  3. Text material
  4. Drawings and site plans
  5. Construction and site photographs
  6. Damage photographs
  7. Geotechnical reports
  8. Environmental assessment reports
  9. Maintenance records
  10. Weather reports – usually rainfall

Additional published documents almost always researched by a professional engineer include:

  1. Legal surveys and descriptions
  2. Land development and drainage plans
  3. Aerial photography of the area of the site
  4. Topographic and contour maps
  5. Surficial and bedrock geology maps
  6. Agricultural soil maps
  7. Hydrological maps and studies
  8. Hydrogeological maps and studies
  9. Flood plain mapping
  10. Mining activity mapping

Documents like these are often studied a number of times during the different stages of an investigation.

Form hypothesis and plan investigation

Information from the documents along with an initial site visit and visual assessment enables the professional engineer to plan the investigation based on what he thinks caused the failure or accident – his initial hypothesis.  Investigations are designed to confirm, revise, or refute the initial hypothesis.

The assumptions made, and their validity, underlying the professional engineer’s initial thoughts on the incident are identified and documented. 

Implicit in the most thorough investigations is an effort to also prove something did not occur in some other manner.

Well planned investigations are sometimes set out as follows:

  1. Task. Identify and describe each task.
  2. Purpose.  State the purpose of each task - what is hoped to be learned.
  3. Data.  (Later, describe what is actually learned, the data gathered).

This simple format enables the investigation to be described in detail later.  It also facilitates development of a timeline of the forensic investigation.

The format is much the same as a “work breakdown structure” in the field of project management.  The “work” in this case is the forensic engineering investigation that has been “broken down” into different tasks.

Determine before/after scenario

In checking the hypothesis, engineering investigations determine the before/after scenario (see Introduction):

  1. The nature of the area the structure is in and the ground beneath the structure
  2. How the structure was built initially, and its conformance to the design and construction plans
  3. What took place during the failure or the accident, and,
  4. The nature and extent of the damage, inadequate performance, or injuries

2. Visual Assessment

Visit and visually assess site

This step involves visiting the site as soon as possible after the failure or accident.  The professional engineer walks and pokes around the site – kicks the tires in a sense, to get a feel for where things are and the nature and extent of the damage, and examines exposed surfaces.  It’s a very simple task – not very technical at all, but invaluable in getting a feel for the scene and bringing the documents to life.

It helps to dictate to a smartphone or Dictaphone what is being seen and done during the visual assessment.

Sketching and measuring what seems to be relevant is started at this early stage.  Measuring, testing, and quantifying in a number of different ways often characterizes an investigation carried out by a professional engineer.

Photograph and videotape site

Photographing and videotaping the failure/accident site and the failed structure is an important initial step, and the sooner the better before remedial work alters conditions.

Equally important is a caption or descriptive note for each photograph stating:

  • What was photographed/videotaped
  • The position of the camera and direction pointed
  • Why the subject/object was photographed
  • What to look for in studying the photograph/videotape, and,
  • The date and time.

Interview witnesses

Interviewing witnesses to the failure or accident or the conditions existing beforehand is also an important initial step.  It should be done as soon as possible after the incident while memories are fresh and site conditions unchanged.  Record names and addresses in the event the witness must be called to testify at a hearing later.

3. Field Investigations

Describe the failure or accident

This step records a description of what happened during the failure or accident based on the comments of the witnesses interviewed and information from the documents.  Talking with people who were there and saw or experienced the failure if it was a sudden collapse of a structure, or an accident, is particularly valuable to the description.

Survey and document the damage to the structure

This step involves recording the damaged condition of the structure that has collapsed or does not perform properly.  The condition is recorded by means of tasks such as the following:

  1. A visual examination and description of the structure’s condition,
  2. Measuring the extent and location of the damage, and,
  3. Photographing and videotaping the damage.

This should be done as soon as possible after the failure before data and evidence are altered or lost.  The information enables a before/after comparison to be made after the next step is completed.  This type of comparison is often quite helpful as noted.

Determine how the structure was built

How the structure was built, whether or not it conformed to the design, and the adequacy of the design, is determined at this stage.  Also, whether or not the design and construction conformed to the standards of the day.  This information is obtained from the design and construction plans.  Also from research of building codes and industry guidelines existing at the time and checking these against the structure on site.  Tasks involved in this step include the following:

  1. Obtaining copies of the design and construction drawings – often quite similar
  2. Checking that the design conforms to the building code and good engineering practice
  3. Checking that the construction drawings conform to the design
  4. Obtaining a copy of the as-built drawings – drawings that record changes made during construction for various reasons
  5. Checking that the existing structure conforms to the as-built drawings.  This involves examining and measuring the different components of the structure.  It often involves taking things apart or using remote sensing techniques to detect what is below the surface.  To facilitate this examination, drawings of the damage might be superimposed on the as-built drawings.  This superimposing would eventually be done during the data analysis (see below)
  6. In the absence of drawings – often the case for older structures, measure the structure and prepare drawings, and then superimpose sketches of the damage

How many of these tasks are carried out and in what detail depends on the situation, the structure, and the failure.  Sometimes very little of the above is done.  Sometimes it’s enough just to measure and prepare sketches of the damage and view and study the structure with these sketches in hand.

Determine the site conditions

The site is the area the structure is in and the terrain beyond the site including other structures.

The site conditions of interest at this stage of the forensic engineering investigative process include:

  1. The lay of the land; the topography
  2. Surface features like bedrock exposures, sinkholes, and wet land
  3. Drainage features like ponds, lakes, and water courses (hydrology)
  4. Subsurface and foundation soil and rock conditions (geotechnology)
  5. Groundwater conditions (hydrogeology)

Investigating and determining site conditions includes:

  1. Photographing and videotaping the site
  2. Aerial photography and map making
  3. Topographic and elevation/contour surveys
  4. Drainage and groundwater studies
  5. Geotechnical and foundation soil and rock investigations
  6. Environmental assessments
  7. Field tests like skid resistance tests, plate load tests and pile load tests
  8. Accident reconstruction

Detailed topographic and elevation surveys are usually made when the failure of a building or a civil engineering structure, or the cause of an accident, is thought to involve the terrain in which the site is located.

Drainage studies (hydrology, hydrogeology) are made when surface or groundwater may have been a factor in a failure or an accident.

Geotechnical and foundation investigations may be necessary if the cause of the failure of a structure appears to be in the foundations or the subsurface soils.

Full scale field tests and accident reconstruction may be carried out.  This is done when these methods are assessed as the most reliable means of gathering data on the effects of the terrain, and features in it, on the failure or the accident.

4. Laboratory Investigations

At this stage in the investigative process, it is often necessary to carry out laboratory tests.  These would determine the chemical, physical, mechanical, strength, and/or drainage properties of materials used in construction at the site of a failure or an accident.  It might be necessary to analyse the toxic fumes emitted by a compound or product used in construction.

Typical materials used in construction are soil, rock, steel, concrete, wood, plastic, adhesives, asphalt, and masonry products.

Composite materials like asphalt or reinforced concrete can be taken apart in a laboratory to determine how the material was formed.  For example, the location, type, and size of reinforcing steel in a reinforced concrete slab that failed.

5. Research

Desk studies and leg work

To some extent, research studies during a forensic engineering investigation – desk studies in some engineering disciplines, are on-going like document review.

The work often involves literature searches, telephone and internet work, and leg work to sources outside the office like libraries and the offices of persons to interview and consult with.

It also involves research and study of aspects of the engineering investigation that have assumed some relevance.  For example, past mining activity in an area, the standard of care at the time the structure was designed and constructed, the shrinkage properties of a fill material, and the different modes of failure of a soil-steel bridge.

Research also identifies and gathers together all information in appropriate categories relevant to the investigation of the failure (see Document Review above).  This would be information usually not contained in the documents provided by counsel during the initial briefing.  Information like original construction and as-built drawings, geotechnical and environmental reports, and published mapping of the area.  Availability of the material would be determined and copies obtained if possible.

Also during this step in the forensic engineering investigative process the need would be identified for additional engineering and scientific specialists to investigate some aspect of the failure, and study relevant findings.  Specialists would be identified, contacted, and conferred with about their possible contribution, and retained if necessary.


Of particular importance during the research stage would be the identification of building codes and industry guidelines.  Also the standard of care followed at some period relevant to the design and construction of the failed structure, or the structure(s) involved in the accident.

Identify building codes and industry guidelines

Identify applicable government and industry codes, standards, regulations, and guidelines.  Include national and international codes, etc, that are relevant to the failure or accident and relied on locally.  Search and identify technical papers and state-of-the-art reports that are relevant to the problem.  Obtain copies and review this material.

Identify standard of care

This could be an important task during a forensic engineering investigation if the findings might be presented during a more formal dispute resolution process or at trial.

The standard of care is the standard commonly applied by professionals or other workers practicing the same discipline or trade in the same area at the time the structure(s) was designed and constructed that was involved in the failure or accident.

Identifying the standard can be quite simple or very involved and time consuming.  It involves interviewing other professional engineers and/or workers practicing in the area at the time the structure was designed and constructed to determine the procedures they followed and the standards they employed.  If there is wide variance you would speak with more people until you feel satisfied you know what the average is.

If there were two small firms practicing in the area at the time, as was the case for a soil-steel bridge failure that I investigated, then it’s easy.

On the other hand, as in another case, if there are 11 different types of firms and associations playing a part in the design and construction process associated with an accident – providing different products and services to the construction process, then it’s difficult and time consuming.  You would need to identify and speak with a number of representatives of each type of firm and association – potentially dozens of people, to be satisfied you understand the process as followed at the time and the average standard of care with which this was done.

6. Follow-up Investigations

This task of carrying out one or more follow-up investigations results from the need to “follow the evidence”.  This concept hardly needs explaining to counsel.  It is equally important in a forensic investigation.  Data will be gathered and evidence uncovered during a previous investigation that suggests another line of enquiry should be followed up or another area investigated.  I think this would be like cross-examination during discovery uncovering evidence that suggests a new line of questioning.

Implicit in the fact that there might be evidence that should be followed up is the possibility that the initial hypothesis on the cause of the failure or accident might need to be revised or rejected completely.

The possibility of the need for follow-up investigations is a fact of life during forensic engineering investigations.

7. Data Analysis and Formulation of Opinion

This is one of two or three final, important steps in the forensic engineering investigative process.  Lots of data is good but you’ve got to do something with the data – draw meaning from it, to serve the justice system.

Data from one stage looked at critically

In analysing and reasoning to a conclusion, the data from any one stage of the investigation is looked at critically – taken apart, in a sense, and each part looked at carefully, and how they are related and their interaction examined.

Identify typical modes of failure?

The data is also looked at closely to see if it is characteristic of or associated with a mode of failure or a cause based on past experience and/or mathematical calculation.  Professional engineers have identified and published typical modes of failure for the various structures in the built environment.  These are available for review and guidance to the forensic engineer during a forensic investigation.

Data from other stages looked at critically and for corroboration

The data from other stages of the forensic investigation are similarly looked at, and also studied to see if there is corroboration of conclusions between stages.  Pattern is looked for within individual data and amongst different sets of data.  And if there is a pattern, considering if it is typical of a known cause/mode of failure.

Draw conclusions and confirm, revise, or refute hypothesis

At some point, conclusions are drawn from the analysis and the hypothesis confirmed, revised, or refuted.  If revised or refuted then a new hypothesis is formed and this investigated with follow-up forensic investigations.

If the initial hypothesis is confirmed then the cause of a failure or accident has been identified and an opinion can be stated.

Document reasoning

At all points in the analysis the reasoning followed is documented and the basis of the conclusions is recorded.

Easy analysis

Sometimes the data analysis and development of an opinion is quite easy.  For example, when field work uncovers a concrete floor slab that is supported by irregularly spaced columns, and the particular type of slab that’s in place beneath the structure is actually required to be uniformly supported.  Then it’s easy to hold the opinion that the floor slab is inadequately supported.

Complex analysis

At other times it’s complex.  For example, when there are more than 20 possible modes of failure for the collapse of a soil-steel bridge.  When the collapsed bridge is not available to examine, then the available data must be analysed for each mode and the cause identified by a process of elimination.

Mysterious analysis

Sometimes it’s mysterious.  Why is there a toxic odour in the concrete enclosed lower level of a structure and the lighter-than-air fumes are not detected in the timber framed upper levels?  A chance remark about timber structures “breathing” – are more pervious, in a sense, in engineering terms, solves the mystery as to cause.  The fumes in the upper levels diffuse through the exterior timber walls to the outside of the structure, and also through open doors and windows.

8. Repair and remediation

Often times near the completion of a forensic engineering investigation there is a need to plan and design repair of the damaged or failed structure, and then estimate the cost of the repair.  This repair cost contributes to an evaluation of the damages claimed in a lawsuit.  Occasionally the repair is constructed involving engineering supervision and inspection costs, which also contribute to the damages.

9. Report

Types of reports

The report, in particular, the written report, is an important step in a professional engineer’s investigation of a failure or an accident.  It is an objective documentation for the judicial system of the methods used during the investigation, the data gathered, the analysis of the data, and the reasoning to an opinion on cause.  It’s importance is highlighted by the fact that civil litigation rule changes in some provinces are limiting discovery of the expert.

The results of a professional engineer’s investigation of a failure or an accident are presented in:

  1. Oral reports,
  2. written report, and,
  3. Occasionally, one or more supplementary reports

Oral report

If possible, an oral report is given to counsel as soon after the documents are read, an initial site visit and visual assessment completed, and an initial hypothesis formed as to cause.  The report will indicate the direction the investigation appears to be leading.  This will give counsel an early indication as to whether the professional engineer will serve as a consulting expert or as a testifying expert.

Written report

A written report is provided at completion of the investigation.  It is prepared on instruction of counsel for the court and judge and submitted to counsel.

Serious thought must be given to having a written report prepared. This is because non-technical counsel and judges are wordsmiths and benefit from well documented data and argument – and usually like well written reports as I have found on more than one occasion.  Else why are civil procedure rules being struck to encourage the preparation of reports and limit expert discovery?  To save time and expense I’m sure but I also suspect because the judicial system likes a well written report.

I know of two cases where junior counsel decided against well prepared reports.  In the one case because of the perceived expense by counsel – and yet it was the first thing the judge asked for, and counsel’s case struggled thereafter, cost more, and may have resulted in significantly lower damages being awarded.

In the second case, counsel submitted a report containing the results of interviews.  The interviews resulted in a poorly prepared report because there was no evidence to validate the interviews which I understand constitutes hearsay in law.  Counsel neglected to call witnesses supporting the hearsay evidence and lost his case.  Both cases seemed to be open and shut cases for the counsels involved.

Supplementary reports

The need for supplementary reports might depend on whether or not new evidence is found during discovery, in follow-up investigations, or presented in rebuttal reports.

Reports, in general, might identify appropriate graphics, models, demonstrations, etc. to explain the investigation and findings to lay technical people.

Report outline

The outline of a report will vary depending on the nature of the failure or accident and the extent of the investigation.  Many will be in chronological order, generally the order of the steps in the forensic engineering investigative process.  The process is a series of investigations and follow-up investigations that in turn are comprised of different tasks.  My reports generally:

  1. Describe the individual investigations and tasks,
  2. State the purpose or reason for carrying out each task,
  3. Identify the data obtained from each investigation,
  4. Document the analysis and reasoning and comment on the validity of the initial hypothesis,
  5. If applicable, report on and document the analysis and reasoning arising from follow-up investigations confirming a final hypothesis, and,
  6. Draw conclusions and formulate an opinion


(This update of an item posted in 2012 identifies investigative tasks like assessing the standard of care existing at the time a structure was designed and constructed or an accident happened.

The update was actually prompted by a long and very difficult assessment of the standard of care in a case, and the realization that assessing standard of care was an important – and sometimes difficult, step in the forensic engineering investigative process.

The update also provides sources in the following References for follow-up and gives data in an Appendix on the difficulty of estimating the cost of forensic engineering investigation)


The foregoing is based on several sources in addition to my own experience.  The citations are not complete:

  1. ASCE, Guidelines for failure investigation, 1989
  2. ASCE, Guidelines for forensic engineering practice, ed., Gary L. Lewis, 2003
  3. ASCE, Guide to investigation of structural failure, Jack R. Janney, 1986
  4. Personal communication, Jack Osmond, NSPL, Affinity Contracting, Halifax
  5. Meyer, Carl, ed., Expert Witnessing; Explaining and Understanding Science, 1999
  6. Steps in the civil litigation process, posted August 28, 2012
  7. The cost of forensic engineering investigation, posted November 1, 2012
  8. ASFE, Association of Soil and Foundation Engineers, Expert: A guide to forensic engineering and service as an expert witness, 1985
  9. Ratay, Robert T., ed., Forensic Structural Engineering Handbook, McGraw Hill, 2000
  10. Day, Robert W., Forensic Geotechnical and Foundation Engineering, McGraw Hill, 1999


(The following is adapted from a posting to this blog site on November 1, 2012 entitled, “The cost of forensic engineering investigation”)

Difficulty estimating the cost of forensic engineering investigation in Atlantic Canada (the items in bold are the main steps in a forensic engineering investigation).

The following is a subjective assessment of the difficulty estimating the costs of the steps in the forensic engineering investigative process (see foregoing item).  The more difficult the step the less accurate the estimate.

The cost assessment at the start of an investigation assumes the request is made of a professional engineer after he has been contacted, the failure briefly described, and the documents identified that counsel will provide.

The assessment is based on my experience in the forensic engineering investigation of failures in the built and natural environments, and fatalities and personal injury accidents, in Atlantic Canada and overseas:

Difficulty estimating costs

  1. Document review ………………………..………………..…………………… Easy
  2. Visual assessment
  3. Visit and visually assess site ……………………………………………. Fairly easy
  4. Photograph and videotape site …………………………………………. Fairly easy
  5. Interview witnesses ………………………………………………………..… Difficult
  6. Field investigations
  7. Describe the failure or accident…………………………………………. Fairly easy
  8. Survey and document damage to the structure …………………… Fairly difficult
  9. Determine how the structure was built ………………………..…. Easy to difficult
  10. Determine the site conditions ……….…………………………..……. Very difficult
  11. Laboratory investigations …………………………………………… Very difficult
  12. Research
  13. Desk studies and leg work ………………………………………………….. Difficult
  14. Identify codes ………………………….………………………………. Fairly difficult
  15. Identify standard of care ……………….………….. . Fairly difficult to very difficult
  16. Follow-up investigations ………………………………………………. Impossible
  17. Data analysis and formulation of opinion ………………..………. Very difficult
  18. Repair and remediation ……………………………………..……………… Difficult
  19. Report ………………………………………………………………………… Difficult

Add to this difficulty of estimating the costs of a forensic engineering investigation, the difficulty of estimating the costs of the role of the expert in the different stages of the civil litigation process.  This compounds the problem further for counsel and the expert.

For example, how, at the start of an action, do you estimate the cost of answering the questions posed under Rule 55 (in Nova Scotia) not knowing how many there will be nor their complexity?

I was asked in a case not too long ago to answer 46 numbered questions submitted by opposing counsel.  On counting, and including important sub-questions, there were actually 77 questions.  The cost of answering these questions was approximately 13% of the total cost of my involvement as an expert in this litigation.


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