[ Technical Illustration Page ][AEC Home Page][ CAD Computer Page ][ Site Map ][ Visualization FAQ ]
FORENSIC GRAPHICS
The Art and Science of Graphic Investigation Work
Copyright1995 © The Art Engineering Company
By Michael Bloomenfeld
The Investigation Begins:
In the initial stages the graphics investigator should accompany the
primary investigators (engineers, police, fire, medical and insurance
examiners) to the disaster site and begin a visual and photographic
survey of the entire building or facility footprint. Using measuring
(and data acquisition) equipment, the primary dimensions of the post-
incident structure, machine or site are determined.
Background:
The graphic investigation specialist should be technically oriented
and have a good basic engineering and construction background in
order to understand how a structure or building facility goes
together. He should be familiar with CADD (Computer Aided Design and
Drafting) and optical field survey equipment. For example, he should
be able to work safely at a post-fire site without disturbing evidence
and, if necessary, help direct personnel and equipment to uncover and
document evidence and arrangements around the origin area much like an
archeological excavation. It is important to locate datums or
semipermanent reference markers which will be useful for offset
measurements and show up in photo records
Creating the Field Notes File:
The preliminary plan or field sketch can include such data as measured
lengths, widths, heights, north bearing, distances, marks, witness
locations, discolorments, furnishings, appliances, machinery and burn
or explosion behavior patterns. Doors, windows, vents, valves and
switch positions are noted. Electrical and HVAC (heating,
ventilating, air conditioning) systems as well as clock and instrument
dials are also documented.
Using the Field Notes File:
In all, a good field notes file is created which can provide adequate
reference information permitting the drafting board work at the office
to be completed simultaneously with the investigation reports.
At the office, under the direction and coordination of the project's
chief investigator, various approaches and types of drawings are
created. For simple reports, a horizontal floor plan sketch showing
the cause or origin location may be all that is required. In most of
the hundreds of small residential and commercial fires and accidents
encountered this is all that is required.
In the more complicated or subrogated cases more details are required.
We try to stay with very basic orthographic diagrams such as simple
schematic line drawings and intentionally expose only as much
information as required to eliminate distraction or confusion. These
flat, one dimensional maps are sometimes enhanced with careful use of
color or shading.
From Field Notes To Working Drawings:
The next phase may be twofold. Initially, a slightly more complicated
drawing may be required to illustrate the failure in question. These
may include vertical plane elevation views, a three dimensional
pictorial or a CADD model (as will be discussed later). Also, the
engineering staff may require measured or technical drawings for fuel
load quantities or char studies, for example.
These "working" drawings are executed in the typical drafter's
language, a kind of visual shorthand that would be confusing and
tedious for most people to read but provide useful and organized
information. In essence, we may be recreating the construction prints
of the destroyed building or failed object. Facilities or apparatus
may be designed as required for innovative or standard testing
procedures.
Field Office Investigation and Research:
The second phase begins by establishing an on site field office in a
trailer or site facility to continue the research and investigation.
All pre-incident plans and diagrams of the subject structure or device
need to be collected. This may include contacting the owner, renter,
facility management, local or regional building departments for codes
and permits, Sanborn tax assessment maps, and old pre-incident photos
or videos (local news media may be helpful here). Remodeling or
alteration drawings and specifications with addendums and change
orders may be available as well as fire police reports which may have
relevant sketches. Surveyed plot plans, aerial and satellite
photogametry, inspection reports, equipment maintenance schedules,
assembly drawings and catalogs, etc., may also be used. The operation
may include specimen and sample recovery, tagging and storing
evidence, and site security.
If a case is to be litigated, depositions and interrogatories may have
helpful witness exhibits such as descriptions, photographs and
diagrams.
Architectural and engineering plans and specifications that describe
the "as built" condition of the property with code and profession
stamps are very important information sources to review.
Reading The Plans And Drawings:
Once the information has been gathered from such sources, an analysis
to sift through the data is required. In order to perform this, the
graphics investigator should be familiar with all the conventional
symbology of many disciplines. He should be able to read any visual
shorthand that is the language of the drafter's and designer's work.
The style and handwriting may indicate the degree of professionalism
gone into the project. The layout and organization of the plans may
indicate how much thought and planning preceded construction.
Finding When And Where Things Go Wrong:
Today, with fast track management and construction techniques,
projects (especially very large ones) are being assembled in the field
by subcontractors concurrent with code agency approvals. This
increases the possibility of defective apparatus arrangements or
installations that fail.
For example, some safety systems may preclude or nullify others. The
earthquake seismic separations in the MGM Hotel towers transmitted
dangerous toxic smoke to the rooms resulting in horrendous loss of
lives. In adequate shop drawing reviews permitted the bolt failures
of the concrete "skyways" at the Kansas City Hyatt-again with large
loss of lives. The Cypress Freeway collapsed because of marginal
seismic design.
Effectively Reviewing All The Documents For Facts:
The process of examining plans and drawn documents as evidence demands
skill and patient exactitude. I tend to review the complete set
quickly to get the feeling for the project and then return to the
first sheet for in-depth study.
The title block (if there is one) contains much valuable information
on who made the drawings and when they were executed. It is important
not to confuse pre-incident remodeling or alteration drawings with
post-incident remodel drawings and looking for who and when on
approvals and revision as well as checker's comments. Find out what
professional registration or code agency approval stamps are present
or required (i.e., sprinklers not approved for high stacked or
combustible fluids). Also, we must know if the drawing had been
reduced, thus changing the scale. Even the blueprint, diazo or
copying process may give us a clue as to the age of the structure.
For example, an aging and complicated inner-urban retail and
commercial structure had been remodeled and subdivided numerous times
since 1909. Some remodels even restored the original configuration
but changed the type of interior structural wall system. Using
ancient building department inspector records, plans and permits, we
were able to create an evolutionary series of drawings which showed
how the fire spread and pinpointed ownership responsibility.
Distributing Working Preliminary Drafts:
This example also brings up the importance of accessibility: drawings
and illustrations must be made available for client and staff review
as the case develops. Certainly, the expression "a picture is worth a
thousand words" is applicable here. "Progress print" or "preliminary"
copies should be stamped, dated and displayed for client conferences.
As a communication tool these drawings save many hours of unnecessary
meetings. CADD generated drawings must be cataloged and time dated. I
never mind having my shoulder looked over at a daily "mini-drafting
board" meetings which keep jobs flowing smoothly.
Developing more detailed pictorials:
Once the data gathering has been accomplished and the analysis
performed, the forensic graphic specialist must develop multi-
dimensional pictorials which clearly illustrate the information
requested by the legal consultant and determined by scientific staff.
Implementing a CADD model may be appropriate. (See "Managing
Investigation Graphics by MB)
There are several types of pictorials which are common and applicable
to investigative procedures. Because of the interesting and very
important information which crystallizes through the graphic process,
the graphic investigator should understand the skills and theory of
"how we see" or the bio-mechanics and psychology of visual perception.
Investigation and the Classes of Pictorial Graphics:
The first type or primary group of pictorials are the paralines.
These are simply drawings that project surface planes to indicate
depth. These are called axonometric drawings and are very useful
because they can be shaded and scaled and are quite simple to
construct. They provide accurate information and with minimal shading
are easy for most people to "read".
The most popular is the 30 degree isometric. Often used as "exploded
assembly" drawings that "float" out walls or parts to separate
objects, they give an immediate visual sense of where and what is
happening without confusing dialogs and minimal texts. This technique
is also good for details and cross sections.
One caution here is to remember isometrics only mimic reality, and it
is a geometric exercise which does not exist as we see. (nature
abhors straight and parallel lines.) Without properly weighted line
work at edge surfaces or shading, the drawing may reverse or turn
themselves inside out or cause other uncomfortable spatial illusions
which often confuse observers.
Oblique projections are similar to the axonometrics and are useful
because one may work directly and rapidly from an existing plan or
orthographic to create a bird's-eye view of the action. Obliques tend
to excessively elongate wall surfaces but are good for quick trace
studies of arrangements. Again, one must use care that the drawing is
absolutely clear and does not become a meaningless abstraction.
Confusing a client or viewer must not be permitted.
Another class of pictorials are the perspectives. They are far more
realistic than the axonometrics or obliques because they show things
as the eye would see them. This would seem ideal but experience shows
that objects seen in perspective may cover, block, foreshorten and
otherwise distort and distract from useful information.
The main elements of perspective contain unique, interesting and
valuable information for forensic graphic work. It is of utmost
importance to have a working familiarity with the rules of
perspective.
What The Witness Observes:
Witness views can be created that can accurately determine what was or
was not seen. Photographs can be analyzed as per location, distance,
sun time and point of view. CADD models may be examined using observer
station points and clipping paths.
There are three types of perspectives: one point parallel, two point
oblique and three point angular. The simplest "one point" type will
be considered to demonstrate the kind of information and problems
which will appear.
The (witness or even fictitious) observer's location is determined and
called the station point. A cone of vision of 60 degrees is created
for the observer's direction with a field of view along the line of
sight. A picture plane frames the object or scene. A horizon line
gives the altitude of view and vanishing points are established to
which all receding lines converge.
We now have the basic elements that provide measured data that can be
manipulated geometrically or mathematically to create a dimensioned
grid. Objects can now be introduced on the grid in extended height,
width or depth. The developing appearance of the picture is analogous
to knowing the "right questions" to ask in problem solving.
As the various types of forensic illustrations develop, materials and
arrangements can be identified. Distortion can be controlled better
than with lens photography. The structural skeleton or hidden objects
can be revealed or prominently displayed. The scene can be recreated
very closely to the time of the incident. Ultimately, well thought
out presentation graphics can be a powerful tool in an engineering
investigation, court judgment or successful marketing decision.
Conclusion:
In a future paper, I will discuss the use of graphics in witness
interviewing, color, psychology, overlayering, digital image
enhancement, animation and reproduction. More importantly, we should
look at how CADD/GIS and computer technology has changed the way
industry creates and produces and how this affects forensic science.
Published in San Francisco Lawyer, Plan and Print Magazine
Please call 1-650-854-5535 or comment by email: macbloom@aol.com
AEC Home Page www.artengineering.com]
[ Technical Illustration Page ][ CAD Computer Page ][ Site Map ][ Visualization FAQ ]