The correct answer is: (A) Admissible, because it is relevant to a causal connection between the dog's ailment and the medication.
Relevant evidence is evidence that has any tendency to make a fact that is consequential to the litigation more probable or less probable than it would be without the evidence. A civil litigant may attempt to introduce evidence of prior similar incidents (or the lack thereof) as circumstantial evidence to support the proponent's claim or defense. As a general rule, most courts will not admit evidence of prior incidents as proof of a defendant's negligence and will not admit evidence of the lack of prior incidents as proof that a defendant exercised due care. The probative value of such evidence is simply too weak when balanced against the risk of unfair prejudice and a waste of court time. However, if the evidence is offered to prove: (1) that a dangerous condition existed; or (2) that the defendant was aware of the dangerous condition, the evidence will be admissible on such grounds. Here, evidence that five other dogs treated with the same drug had suffered blood clots identical to the dog owner's dog tends to prove that the medication at issue caused the dog's injuries. This causal link is a necessary element of the dog owner's cause of action, and so the evidence is relevant and admissible if there is evidence that the medication caused the same injury to other dogs under circumstances materially similar to the case at hand.
(B) Incorrect. Admissible, because the witness is a qualified expert as the head of a veterinary clinic.
It is true that the fact that a witness qualifies as an expert permits him to testify in the form of opinions that would otherwise be inadmissible. Here, however, the witness would be testifying that he treated other dogs with medical conditions similar to the dog owner's dog. Thus, his testimony would not be opinion testimony, but testimony by an eyewitness. Furthermore, even if the witness is a qualified expert, that alone will not render his testimony admissible. To be admissible, expert opinion must be relevant to a material issue in the litigation.
(C) Incorrect. Inadmissible, because the testimony regarding the other dogs constitutes hearsay.
The witness's testimony is not testimony of an out-of-court declaration and thus cannot constitute hearsay. The witness would be testifying as to events that he perceived and in which he participated, not what other people told him.
(D) Incorrect. Inadmissible, because it violates the best evidence rule.
The best evidence rule refers to the requirement, in certain circumstances, that the content of a document or recording be established by production of the original (or a copy thereof). The witness's testimony does not seek to prove the content of any documents or recordings. As such, the best evidence rule does not apply.
