Plaintiff was given an umpire’s mask by a representative of Defendant at an annual retreat for Major League Baseball umpires.  The mask had a new type of throat guard which angled forward as opposed to extending straight down.  Months later while wearing the mask, Plaintiff was struck by a foul ball, suffering a concussion and damage to his inner ear.  Plaintiff developed moderate hearing loss, which was permanent, as a result.  Plaintiff sued Defendant, claiming the design of the mask was defective.  A jury found for Plaintiff on all counts.  On appeal, Defendant argued that testimony by Plaintiff’s expert witness was wholly deficient, that the jury should have been given an instruction for assumption of the risk, and that the evidence was insufficient to support the verdict.  Defendant contended that Plaintiff’s expert had not performed his own tests or adequately explained every aspect of his reasoning.  The D.C. Court of Appeals affirmed the trial court, noting that an expert is not required to perform his or her own tests and that expert testimony should be excluded only where it consists of mere assertions.  Defendant could have explored any deficiencies in the expert testimony on cross-examination or in closing argument.  The Court of Appeals also rejected Defendant’s contention that the jury should have been given an instruction for assumption of the risk.  To get such an instruction, Defendant had to show that Plaintiff was aware of the specific defect and its associated danger.  Defendant could not merely allege Plaintiff was aware of the defect and danger because he was a professional umpire.  Finally, the Court of Appeals held that a reasonable juror could have found that the product was defective using the “consumer-expectation test.”