In Crown Life Ins. Co. v. Estate of Gonzalez, 820 S.W.2d 121 (Tex. 1991), the court held that a court of appeals should grant presubmission leave to supplement the record absent a finding of unreasonable delay.
The court reasoned that appellate courts must construe former Rule 55(b) TEX. R. APP. P. 55(b) (Vernon 1997) liberally so their decisions "turn on substance rather than procedural technicality." Crown Life Ins. Co., 820 S.W.2d at 121.
The court held that the rule applies whether parts of the record were omitted by mistake or at appellant's request, and noted that, while leave to supplement post-submission is often denied, seldom is a party who otherwise timely files a record denied presubmission leave to supplement.