Here, however, the Court assumes without deciding that Henderson's modifications did change the substance of the assignments. In such circumstances, an appellant can only escape default if her brief adequately addresses the issue raised by the original assignment. See White v. Commonwealth, 267 Va. 96, 103 (2004). The Court finds that to be the case here, which is especially fortunate for Henderson because she ends up winning on the merits.
Not every appellant is so lucky. The Court will never address new issues raised by an improperly modified assignment of error. For example, in Hudson v. Pillow, 261 Va. 296, 302 (2001), the Court declined to consider Hudson's second assignment of error in her opening brief after finding that it was "entirely different" than the original.
Although some litigants, like Henderson, get away with modifying assignments of error mid-appeal, there is no reason to try it yourself. The Court will not consider any substantive change you make. At best, you'll draw the Court's ire. At worst, you risk procedually defaulting your client's appeal. Just don't do it.