Evidence Retention from Event Data Recorders



Charles C. Roberts, Jr. Ph. D., P.E.


Event data recorders are typically electronic devices that store information received from sensors connected to the device. An event data recorder is often referred to as a “black box,” a familiar recording device found on many large passenger aircraft. Event data recorders are now being designed into many other products to aid in diagnosing problems that may arise with usage of the product. Automobiles, electronic panels, alarm systems and some appliances are equipped with event data recorders. When a loss occurs, it is becoming more likely that some evidentiary information concerning the loss will be recorded on some device. Typical recorded data may be the time a heat sensor activated in a fire alarm panel, the number of loads handled by a clothes dryer, or the speed of an automobile prior to a collision. The following three examples illustrate the type of data retained in “black boxes” and their significance. It should be noted that this article deals with numerical data retained and not visual data retained from the prolific surveillance camera.

Dryer Fire

Many high end appliances are equipped with event data recorders and internet access. Manufacturers offer services to customers to monitor and diagnose their appliances remotely. Figure 1 shows the internal components of a clothes dryer with a fire origin to the left side of the photo. Luckily, the event data recorder survived the fire.

Figure 1


Figure 2a

Figure 2b


A lap top computer was connected to the interface on the dryer, and the screens in Figures 2a and 2b resulted. In Figure 2a, date of manufacture, model number and specifications are recorded. Also the number of hours the dryer had been used prior to the fire was noted at 179 hours, which is a relatively small usage. Figure 2b shows a sensor output, which was the door switch sensor, indicating that the door was open. Other sensor outputs are recorded and may vary in type, depending on the manufacturer. The number of hours used suggests that the appliance had not been run around the clock, which may have significance in a particular case.

Alarm Panel

Alarm system malfunctions are often of interest in large fire losses. Figure 3 shows a typical electronic alarm panel with internal memory for event recording.

Figure 3

Figure 4

Figure 4 is the screen from the readout of onboard memory. The upper arrow shows a phone line failure when attempting to communicate with the monitoring station. The lower arrow shows the time and zone of the fire alarm, which was not communicated with the monitoring service because of the phone line failure. This data is evidence and can be used as a basis for determining who is a target of subrogation.

Motor Vehicles

Present day motor vehicles are equipped with a variety of event data recording devices such as the sending diagnostic module for airbag deployment or onboard memory for trouble code storage.


Figure 5

Figure 5 reveals the data recovered from an automobile “black box” after an accident. Conditions were dry at the time and the vehicle struck another head on. The information shows the vehicle speed to be approximately 46 MPH, one second before impact. The driver seat belt was recorded as ‘unbuckled.”


Many issues have arisen with the advent of these recording devices, one being the ownership of the data. Typically, it is accepted that the product owner owns the data, but one should check with local state laws as to its status. Some data is volatile and may be erased as a result of continued product usage or deterioration. Static electrical discharge can cause computer resets or loss of stored information. Some DTC (diagnostic trouble codes) will be erased after a number of ignition switch cycles. Typically, downloading information from “black boxes” is non destructive, although some diagnostic systems allow erasure of the memory and loss of data. As the existence of information stored in event data recording devices becomes more widely known, the lack of retention of such data is being used as grounds in the assertion of spoliation, which can be a barrier when proceeding with a subrogation related action.