Not according to the Virginia Magazine of History and Biography.
From Wiki
>>Though Casor was the first person declared a slave in a civil case, there were both black and white indentured servants sentenced to lifetime servitude before him. Many historians describe indentured servant John Punch as the first documented slave in America, as he was sentenced to life in servitude as punishment for escaping in 1640.<<
https://en.wikipedia.org/wiki/Anthony_Johnson_%28colonist%29#Casor_suit