Defendant demonstrated prima facie entitlement to judgment by submitting competent medical evidence that neither plaintiff satisfied the serious injury threshold of Insurance Law § 5102 (d) ( Franchini v Palmieri, 1 NY3d 536). Plaintiffs failed to satisfy their evidentiary burden of submitting, in opposition, "objective medical proof of a serious injury causally related to the accident in order to survive summary dismissal" ( Pommells v Perez, 4 NY3d 566, 574). The unsworn medical documentation submitted by plaintiffs was not properly before the court, and thus was correctly not considered ( Grasso v Angerami, 79 NY2d 813). We also note the affirmation by plaintiff's medical expert failed to explain adequately the reason for the 15-month gap in their treatment, and their excuse was not supported by the record.