Expertly Speaking

Drinking and Darting Don’t Mix


Robert T. Lynch, P.E., Principal Collision Reconstruction Engineer

A box truck was double-parked on the right side of a roadway. As a transit bus was passing the box truck, an intoxicated pedestrian stepped out from in front of the box truck and walked directly into the path of the bus. The engineers at DJS were retained by the bus company to reconstruct the collision.

Video from inside the bus captured the events leading up to the impact. According to the video, the pedestrian first became visible approximately 2 seconds prior to contact; however, an analysis indicated there was not sufficient time for the bus operator to perceive, react, and bring the bus to a stop prior to reaching the point of impact. This was an example of a classic “dart-out” case, where the incident was unavoidable for the driver. The pedestrian was crossing mid-block outside a crosswalk (and from an obstructed position), and, as such, the pedestrian was required by law to yield the right-of-way to the bus operator.

No liability expert report was served on the pedestrian’s behalf. The case was set to go to trial at the beginning of January 2022, but settled in mid-December for a minimal amount.

Robert T. Lynch, P.E., Principal Collision Reconstruction Engineer with DJS Associates, Inc., can be reached via email at experts@forensicDJS.com or via phone at 215-659-2010.

continue reading

Wi-Fi Network, Forensics, and Yet Another Way to Determine
A User’s Location


Timothy R. Primrose, Mobile Forensic Analyst

When a device is connected to a Wi-Fi network, it typically stores the credentials for future use, allowing it to automatically reconnect to the Wi-Fi network the next time it is in range. Every time the user leaves a saved location with their cell phone, it disconnects from the Wi-Fi network and automatically reconnects when the user gets home. The date and time of the last auto-connect is stored on the device for each set of Wi-Fi network credentials.

Wifi Log

The preceding table displays the Wi-Fi connection history of an iPhone 8 Plus. The “Last Connected” column displays the last time the device was manually connected to a Wi-Fi network. The “Last Auto Connected” column displays the last time the device automatically connected to the Wi-Fi network. The “SSId” column displays a recognizable name for the Wi-Fi network.

Case Study:

Background – A woman that lived alone was murdered in her home one night. Local law enforcement marked her ex-husband as their first suspect. He claimed that he was at home, watching the Sixers game.

Forensic Analysis – Analysis of the ex-husband’s cell phone showed that it auto connected to the Wi-Fi network of his ex-wife’s home 12 minutes before the time the coroners said she died. His ex-wife’s home is the same place that he called home before the divorce. While the locks had been changed, the internet service remained. The ex-husband’s phone held onto the Wi-Fi network’s credentials and connected to the Wi-Fi network when he arrived at the property, placing him at the scene of the crime, and not at home watching the game.

Timothy R. Primrose, Mobile Forensic Analyst with DJS Associates, Inc., can be reached via email at experts@forensicDJS.com or via phone at 215-659-2010.

continue reading

Scooter Self Stoppage: Electromagnetic Interference with Electric Scooter Controls Cause Injury


John M. Tobias, Ph.D., P.E., CFEI, Electrical Engineering & Illumination Expert

Case Description:

The defendant suffered significant injury while riding on an urban street when the front wheel of an electric scooter braked unexpectedly, propelling them forward over the handlebars of the scooter. Investigating these mishaps, it was found that the scooter braking control is sensitive to external magnetic fields commonly emitted by utility power lines and similar electric utility equipment. The mishap location corresponded to the location of underground power utility equipment. Subjecting the scooter braking control to electromagnetic interference, specifically power frequency (60 Hz) magnetic fields, engaged the braking function. Further investigation revealed that the electric scooter was not properly tested for the effects of external electromagnetic fields on its safety-critical braking controls.

Electric Scooter Control and Braking:

The subject electric scooter had one small-diameter (8-inch) drive wheel at the front and two free-spinning tandem wheels at the rear, interconnected by a platform upon which the operator stands to ride the scooter. Control for the scooter was provided by a handlebar with integral controls for engaging the motor and braking on the right and left handlebars, respectively. The scooter incorporated a liquid-crystal electronic display/control panel, among other controls. Turning the handlebars provided directional control and steering, mechanically changing the angle of the front-wheel with respect to the long axis of the scooter, thereby changing the direction of travel, as with a bicycle.

In this particular case, an integral electric motor in the front drive wheel provided motive force for the scooter and employed what is termed ‘electronic braking’. Electronic braking utilizes the principle of ‘back electromotive force’ or back EMF, which is the converse of the motor function. Essentially, the motor becomes a generator when power is removed, which provides a retarding force. Creating an electrical short-circuit, or high resistance, across the motor creates a large back EMF (electromotive force) that arrests the spin of the integral motor/wheel assembly. In this arrangement there is no friction device, such as disc or drum brakes, for slowing the scooter.

The drive and braking controls are fully electronic. No mechanical links are present between the brake trigger and the drive wheel. Rather, the function of the motor is governed by a microprocessor, using inputs from the handlebar trigger switches for acceleration and braking. As one would expect, software or firmware controls the microprocessor and consequently the acceleration and braking functions. The particular scooter in this case was capable of speeds up to 20 miles per hour.

Electric Scooter Control Sensitivity to Magnetic Field Established by Testing:

Among other tests, including exposure to radio frequency radiation between 20 MHz to 3000 MHz, the scooter was subjected to power line frequency (60 Hz) magnetic fields. Although some of the scooter controls appeared affected by the radiofrequency radiation, the scooter brake control switch was found to consistently respond to external power line frequency magnetic flux density, or magnetic induction, between 0.5 milliTesla to 1.0 milliTesla. When the control was exposed to this degree of external magnetic field, the front wheel of the scooter ‘locked up’ abruptly and engaged the brake light that was affixed to the rear of the scooter.

Scene Investigation:

An electromagnetic survey of the mishap location was conducted by reviewing nearby Federal Communication Commission license holder data, and through measurement. Magnetic fields comparable to what’s needed to trigger scooter braking function were found at the mishap location. Further investigation revealed that underground electric utility equipment (transformers and distribution circuits) was present at the mishap location. The degree of magnetic field near utility equipment and circuits correspond to the current load on the circuit, increasing during periods of high electric demand. So the scooter could traverse the same location without incident on some occasions during low electric demand, but malfunction and trigger the brake unexpectedly on other occasions, such as during periods of high electric demand.

Findings and Opinions:

The electric scooter was subject to abrupt and unexpected braking where magnetic fields were present at the mishap location, in this case a sidewalk in a major urban setting. Marketing materials for the scooter was targeted to urban users, highlighting its advantages and suitability for urban environments. As such, it was not safe to use in its advertised and intended application.

Product safety efforts were inadequate for the subject electric scooter. The US Consumer Product Safety Commission (CPSC) strongly endorses Underwriter’s Laboratories Standard for Safety 2272, entitled ‘Electrical Systems for Personal E-Mobility Devices.’ (UL 2272). That standard, in turn, invokes Underwriter’s Laboratories Standard for Safety 991, entitled ‘Standard for Tests for Safety-Related Controls Employing Solid-State Devices.’ (UL 991). Discovery and research efforts in the case revealed that little to none of the analysis and testing specified by these standards was conducted, although competitors marketing similar scooters did so, listing their products to the UL 2272 standard.

Moreover, exclusive use of front-wheel braking is conducive to loss of control and falling, contributing to the severity of the mishap. Aggressive braking of only the small diameter front wheel of the scooter creates a large mechanical moment about the axle of the front wheel, causing the rider to pitch forward over the handlebars. Consequently, if the brake for the scooter is applied suddenly, (and especially unexpectedly) there is a high probability of the rider falling.

Lastly, the degree of the magnetic field present at the mishap location exceeded the applicable State Public Service Commission guidelines.
Efforts in the case resulted in an equitable undisclosed settlement for the plaintiff.

John M. Tobias, Ph.D., P.E., CFEI, Electrical Engineering & Illumination Expert with DJS Associates, Inc., can be reached via email at experts@forensicDJS.com or via phone at 215-659-2010.

continue reading

Forensic Engineering Investigation of Electrical and Electronic Causes of an Industrial Equipment Failure


Robert Peruzzi, Ph.D., P.E., DFE, Electrical Engineering Expert

The shrink-wrap failures had been isolated to a group of several transistors within the electro-mechanical modules within the equipment, but the root cause of those transistors failing had not been determined. The equipment; however, seller had more than 1,000 units in the field with no similar failures. In addition, the electro-mechanical module manufacturer had more than 20,000 units in the field with no similar failures. Electrical contractors hired by the buyer had measured power quality, and reported no faults found in the three-phase power at the equipment terminals. This paper presents circuit analyses of the failing electro-mechanical module, basics of electrostatic discharge damage and protection, and the root cause of these failures — an electrical code-violating extraneous neutral-to-ground bond in a secondary power cabinet.

Click the link below to review the complete article:
https://journal.nafe.org/ojs/index.php/nafe/article/view/812

Robert Peruzzi, Ph.D., P.E., DFE, Electrical Engineering Expert with DJS Associates, Inc., can be reached via email at experts@forensicDJS.com or via phone at 215-659-2010.

continue reading

Picnic Table Tipover


John R. Yannaccone, P.E., Principal Mechanical Engineer

Incident Description: On a warm summer evening, a family was attending a festival in a municipal park. They had purchased food, found a picnic table where a few other people were already seated, and asked if they could share the table. All was fine as they sat socializing and enjoying the evening. Gradually, people seated at the table began to get up, and as the last person on one side of the table stood, the table, with attached benches, tipped. The remaining woman seated on the other side of the table fell from the bench, landed on the concrete pad, and sustained injury.

Expert Analysis: When an inspection of the table was conducted, well after the incident, the table could not be tipped since there were legs under the attached benches. Photographs taken on the evening of the incident showed these legs were not in place at the time of the incident and had been added to each table in the park. The inspection further revealed the tables, including the one involved in the incident, had aluminum angles screwed to the four support legs. While some of the tables were bolted to the concrete pads with anchor bolts, other tables were no longer fastened to the pads; however, the anchors were still present in the concrete pads.

Since all the tables had additional bench supports added at the time of the inspection, the stability of the tables could not be verified. An engineering analysis of the table design and forces that would be applied by table users indicated the design of the table was such that a person seated alone could apply enough force to cause the table to tip. Further investigation revealed the company, which manufactured them, had two options for installation. The tables could be installed with the legs embedded 18 inches into the ground or shorter legs could be fastened to an anchor or concrete pad/footing. The documents from the time the park was redone showed the tables were purchased with the longer legs and were originally installed in grass areas with the legs embedded into the earth. At some later date, the concrete pads were added to the park and the table legs were cut shorter and anchored to the pads. This attachment was not maintained by the municipality or operators of the park, resulting in some of the tables sitting unanchored on the concrete pads. In this condition, the unbalanced load from a person could cause the table to tip over, as occurred on the evening of this incident.

Result: Once the installation problems and errors were identified, the defense offered a settlement.

John R. Yannaccone, P.E., Principal Mechanical Engineer with DJS Associates, Inc., can be reached via email at experts@forensicDJS.com or via phone at 215-659-2010.

continue reading

Food and Fluid Safety in Healthcare Settings


Stacy L. Donnelly, RN, BSN, Nursing & Nursing Home Expert

First and foremost, regarding food/fluid safety, healthcare professionals need to ensure an individual is receiving appropriate nutrition, hydration, and services to meet their needs. In all settings within the healthcare field, healthcare professionals can rely on a specific process to assess clients and develop care plans to address the specific needs of each individual. This process includes assessments, identification of potential risks, evaluating and analyzing risks, implementing care plans, monitoring, and evaluating the interventions and making changes according to their needs.

According to the American Dietetic Association, “Nutritional assessment is a systematic process of obtaining, verifying and interpreting data in order to make decisions about the nature and cause of nutrition-related problems.” An important aspect of the assessment process for healthcare professionals is to consider the intrinsic and extrinsic factors that can affect an individual. This information can be obtained from a variety of sources including the individual’s records, staff, family, patient interview, and direct and indirect observation. The assessment will help the healthcare professionals define the nature of the problem and set the stage for individual interventions to be implemented.

Once a comprehensive assessment has been completed, healthcare professionals will begin to identify potential food safety risks. The risks may include data gathered by identifying the intrinsic and extrinsic factors. Certain diseases and conditions that are identified as intrinsic factors can increase or decrease an individual’s ability to safely consume both foods and fluids. For example, an individual with cognitive impairments may not be able to properly determine the size or amount of food they can safely masticate, therefore requiring interventions to assist them during this process. The extrinsic factors for this individual are just as important to take into account. This same individual may become easily distracted during eating and drinking. If they are eating in an area that has distractions, they may easily lose track of what they are doing and “forget” to fully chew or swallow their food/fluids, causing an increased risk for choking.

After all potential risks have been identified healthcare professionals will evaluate and analyze the risks. At this point in the process they will take a detailed examination of all the intrinsic and extrinsic factors associated with the individual and develop appropriate individualized care interventions. During the evaluation and analysis of risk, healthcare professionals will carefully determine what intrinsic and extrinsic factors can be decreased or eliminated through interventions to ensure safe food/fluid consumption for the individual.
The development of interventions for individuals in the healthcare setting is key for ensuring food/fluid safety. The purpose of the interventions is to limit the risk of an adverse event. The interdisciplinary team will review the assessments and risks identified and develop an individualized care plan. The care plan will address identified causes, reflect the individual’s goals and choices, and identify specific interventions, time frames, and parameters for monitoring the interventions. There are a variety of possible interventions associated with food/fluid safety which may include:

  • Diet Liberalization
  • Nothing by Mouth (NPO)
  • Dietary Restrictions
    • Low Fat
    • Low Sodium
    • Carbohydrate Controlled
    • The avoidance or addition of certain foods directly related to the individual’s diagnosis and medications.
  • Mechanically Altered Diets
    • Mechanical soft
    • Puree
    • Hand-cut
    • Chopped
    • Thickened Liquids (Honey, nectar, pudding consistency)
  • Assistive Devices/Utensils
  • Supervision

An important aspect to the development and implementation of the individual care plan includes communication between the interdisciplinary team, including both written and verbal. This communication is particularly important for those who do not regularly interact with the individual. For example, when an individual is partaking in an outing away from their traditional setting the persons with them need to be aware of the care plan interventions so they are not served foods or fluids that could negatively impact their health and safety.

Once the interventions have been developed, implemented, and communicated, the healthcare professionals will monitor and evaluate for the effectiveness. The process of monitoring includes reviewing the intrinsic and extrinsic factors, assessments, and observation of the individual. If during the process of monitoring it is determined there has been a change in the individual, or the interventions are not effective, the healthcare professionals may implement new interventions. A consultation by a physician or speech therapist may be appropriate to best determine what interventions could be utilized.

Throughout the settings, supervision plays an important role in food/fluid safety. Supervision will provide safety from the individual obtaining food/fluids that are too hot, of the wrong consistency, that can cause choking, or negatively impact their overall health. In all healthcare settings food/fluid safety is a systematic approach which includes assessments and intervention development/implementation and monitoring from an interdisciplinary team.

Stacy L. Donnelly, RN, BSN, Nursing & Nursing Home Expert with DJS Associates, Inc., can be reached via email at experts@forensicDJS.com or via phone at 215-659-2010.

continue reading
1 2 3 129

Do You Need Help Finding the Right Expert for Your Case?

x