On March 18, 2009, plaintiff Mirna Prieto, 63, a disabled retiree, was driving her car east on Freeway 60 in West Covina with her mother, plaintiff Elsy Semerena, 83, a retiree, as a front seat passenger, when the traffic ahead abruptly stopped. Prieto attempted to stop and was rear-ended by a semi-truck, which was rear-ended by another semi-truck operated by Joise Muniga. Prieto also rear-ended the vehicle in front of her. She claimed to her lower back, while Semerena claimed to her neck and lower back. Prieto and Semerena sued Muniga and CPL Express Trucking Co., Muniga’s employer and owner of the truck. They alleged that Muniga was negligent in the operation of his vehicle and that CPL was vicariously liable for its employee’s actions. The parties ultimately stipulated to a binding arbitration at JAMS. Prieto claimed that she made a sudden stop due to the traffic ahead of her abruptly stopping, but that Muniga caused the chain-reaction collision by failing to slow down and rear-ending the semi-truck that in turn rear-ended her vehicle. She also claimed that these rear-enders caused her to subsequently rear-end the vehicle in front of her. Plaintiffs’ counsel produced the police report of the accident, which placed Muniga at fault, in violation of California Vehicle Code § 22350. Muniga denied liability and initially claimed that the lead vehicle, a BMW, caused the chain-reaction collision by making a sudden stop. However, he later alleged that either Prieto or the semi-truck in front of him made a sudden stop and causing the accident., Prieto complained of a headache at the scene of the accident and was later driven to an emergency room with complaints of neck and lower back pain. She claimed she aggravated a pre-existing condition of the lumbar spine’s disc pathology. Prieto subsequently treated conservatively with chiropractic care and pain management, which she claimed failed. In January 2010, she underwent posterior and anterior fusions at L4-5 and L5-S1. Prieto then contacted a staph infection from the surgery and required 40 days of antibiotic injections. Prieto claimed she is now restricted in certain hobbies, including gardening and walking. Thus, she sought recovery of damages that included $500,000 for past medical costs and an unspecified amount for past and future pain and suffering. Semerena claimed soft-tissue to her neck and back, as well as a minor head injury. She treated with chiropractic care for two and a half months. However, she did not require any additional treatment or make any residual claims. Thus, Semerena sought recovery of damages, including $11,000 for past medical costs and an unspecified amount for her past pain and suffering. Defense counsel argued that Prieto had a pre-existing lower back condition going back over 30 years, which included worker’s compensation claims and multiple slip-and-fall incidents. Counsel contended that MRIs taken of Prieto before and after the accident were identical and, therefore, there were no changes to her lumbar spine. Defense counsel further argued that Semerena was 83-years-old at the time of the accident and that all her were pre-existing.