Both of the injured people should consult with an experienced personal injury lawyer. Lawyer's who do this work generally offer free consultations, and take these cases on a contingent fee basis. Don't assume that you know how the law works, as these cases can sometimes turn dramatically due to the twist of an isolated fact. Good luck.
The author of this post is licensed to practice law in the District of Columbia, Maryland, and Virginia. This post is intended as general information only, and is not provided as legal advice in connection with any specific case, and does not create an attorney-client relationship.
It sounds like you may have several options, including a possible workers' compensation claim. The workers' compensation system provides for payment of medical bills, as well as lost wages. Parking lot cases are often contested. You can get an initial consultation with a work injury attorney for no cost. If you need help getting started, feel free to give me a call. I have a few questions for you, but I believe I can recommend an attorney who can help. 1-800-807-9530.
Two Big points:
Regarding workers comp: Your fiance, but not your step son, may well have a viable workers compensation claim. The Pa Workers' Compensation Act, as interpreted by the courts, affords a "going and coming rule." If the parking lot was truly a part of the employer's premises, and if your fiance was there for purposes benefiting the employer (i.e. showing up for work), she'll have a good argument that this was an injury in the course of her employment and covered under the workers' compensation act. However, it gets "iffy" if she was there for some purpose more of her own, such as simply to pick up her paycheck, etc., and the fact that your step son was with her makes their purpose on the employer's lot a pretty clear question.
Regarding the limited tort problem: Your question indicates that your fiance was a PEDESTRIAN at the time of her accident. Under a case decided about three years ago, pedestrians have FULL TORT rights as a matter of law. She should be able to make a claim against the defendant driver for damages arising from his negligence.
I invite you to call me to discuss your matter further: 215 559 5003
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