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Arson Investigations:

What is needed may be found with an understanding of Burglar Alarm Systems


Neil E. Price
NET Limited Inc.
Independent Security Consultant
4887 Dublin Drive
North Royalton, OH
44133 - 2155

Burglar alarms are primarily installed to detect and report unauthorized entry into a protected location. In general, the design characteristics are typically intended to provide for the ability to detect the opening of selected doors and windows, detect unauthorized or unapproved motion within the protected environment and/or detect a forced attack against structural materials such as glass, wood, metal or concrete.

An alarm system consists of three basic components - Sensors, a Control and Annunciation equipment. The sensors initiate an alarm, the control directs per-programmed system actions and the annunciation equipment warns, or sets forth a visual and/or audible alert which is intended to alert neighbors or monitoring personnel there is cause for concern. All three component parts can be connected by wire, a radio frequency link or a combination of both.

Besides directing a pre-programmed response to sensor activation(s), a control panel manages the prompts necessary to turn the system on or off. In addition, it provides the ability to switch to battery back up power in case of a commercial power failure. If the system is designed, installed and maintained properly, an intruder's attempt at an unauthorized, unlawful or forced attempt at entry should theoretically be detected.

Generally, the desire is to detect and report at the onset of the attempted intrusion - In theory, prior to an actual penetration of the protected area. Short of this early notification, an intrusion must be recognized after the fact as unauthorized or undesired movement/motion or noise within the protected location. These occurrences and the ensuing report are a direct result of detector capabilities, design criteria, and decisions relating to sensor placement and positioning. Report of unauthorized activity may be the result of an attempt to gain entry from the outside, or as in the case of a "stay-behind", a report may be initiated upon an intruder attempting to leave. In either case, with a properly designed system, system sensors should respond to abnormal or undesired activity and a "cry for help" should be initiated.

It is the "cry for help" that is most important in any alarm system. Without the ability to provide notification of unwanted or undesirable activities and the details surrounding a particular event, the detection capabilities are worthless.

When conducting an investigation where an intrusion detection system (burglar alarm) is evident, it is important to first note the system's condition. This is accomplished by a survey and it should be conducted at the onset of the investigation. This survey should ultimately determine a system's design characteristics (strengths and weaknesses) and whether there is any evidence of tampering.

Sensor capabilities and design technology should be understood as they are recognized. Although intended to detect human actions and movement, some sensors also have the potential to detect physical phenomena or respond to changes in the environment that are not necessarily intruder related.

For example, infrared motion sensors operate on the principle that they will detect intruder movement because a human being passing in view of the sensor will introduce changes or new levels of infrared energy in certain pre-selected monitor points. This change in temperature, or recognition of a difference from the norm in one sensor viewing area to another, because of an intruder passing between the sensor and the reference point, is "interpreted" as motion for purposes of detecting an intruder. Significant changes in temperature levels or a sudden rise in infrared energy are, however, not exclusive to just those produced by a burglar.

Do not assume that features available in one manufacturer's model of control are the same as that of another manufacturer, even if they may have the same appellations, physical resemblance or labeling style and colors. Do not assume a particular brand or model of control is always intended to operate the same in all installations. Some features may be options or "add-ons". In addition, do not take for granted that a premise owner understands all the operational aspects of their system. It is not uncommon to find that some system features are not even known by a user.

Alarm systems are not designed to be operated by a unique individual. They are designed to operate solely on criteria established by equipment manufacturer's, system installers and system designers. There is no such thing as a universal alarm system. Moreover, there are too many different equipment manufacturers and system options to allow for assumptions.

Factors that should immediately be taken under advisement when conducting an investigation where a burglar alarm system has been installed are as follows:

  1. Status upon arrival? Are indicator lights on, off, flashing, or steady? What are the colors of the lights that are on? Are there any messages on a keypad screen? If there is a lock, used to turn the system on or off, what is the position of the keyway?
  2. What sensor technologies are employed (e.g. magnetic switches, glass break detectors, passive infrared motion sensors, floor mats, photoelectric beams, etc.)?
  3. Are there any sensors that do not appear to be connected to the control panel (e.g. wires disconnected, batteries missing, transformers unplugged)?
  4. What is the extent or area of sensor coverage?
  5. What is location of alarm control panel?
  6. How is panel secured? Is panel in a secure area, room or closet? Is access to panel restricted? Is panel housing door open, closed, locked, unlocked, screwed shut, damaged, etc?
  7. What is condition of alarm panel itself? Are all wires leading into or entering the panel enclosure connected to the panel? Are all wires that appear to leave the panel (e.g. telephone line or connection to local noisemaker) connected?
  8. Is an auxiliary battery connected to the panel? If so, what is the condition of the battery (e.g. normal appearance, split, cracked, broken terminals, etc.)? If disconnected, what is condition (e.g. charged, discharged below acceptable limits, etc.)?
  9. What is condition of alarm panel fuses? Is there any that have been blown? Are any missing?
  10. If alarm is monitored remotely, is the telephone line connected at all access points up to and including those outside the protected location (e.g. interior terminal blocks, equipment closet punch blocks, ground pedestal, telephone pole, cross box, etc.),
  11. If alarm is transmitted by radio or cellular telephone, is there indication that antenna is capable of radiating a signal? Does transmitter or cellular telephone have power?
  12. If annunciation is local, are wires to bell, strobes or siren intact? Is noisemaker present and in good condition?
  13. How is system activated or deactivated (turned on and off)? If by key, what is resistance to manipulation and/or tampering? If keypad is used, do authorized individuals all have same code or do they each have unique codes? Does system report openings and closings?
  14. Is mechanism to control system (keypad or switch lock) located inside or outside the protected location? Are there built-in penalties for tampering or attempting to spoof the system's operational features?
  15. In the event system is remotely monitored, determine last report of activity at annunciation point and circumstances surrounding transmission of signal. Determine response procedures and if appropriate, obtain a history of alarm activations, repairs and/or service calls for the premise in question.
  16. Endeavor to obtain hard copy records of work products that contain information such as times, equipment brand names, model numbers, dates of repairs or changes in system configuration and installer or repair personnel names.

Understanding the design parameters, the operation, and the reporting capabilities of a burglar alarm system has the potential to help identify possible co-conspirators, possibly establish a time for the activation of an incendiary device and/or assist in determining or corroborating the location where a fire may have started. Understanding how a burglar alarm system is intended to detect burglars or prevent their movement without detection, may in the final analysis, be the key element that helps to resolve some questionable aspects in an arson investigation.



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