Answer:
After his slaveholder owner died
Step-by-step explanation:
Dred Scott was an African American man who was born in 1799 in the United States. He sued his owner for his freedom and that of his wife and two daughters.
In 1846, After Emerson his slaveholder died , he due his master's widow.
He sued his owner when he came back from Missouri where he originally lived , after the owner have him worked in a non slavery states. He sued on the basis that he is in a free state and he supposed to be free. His slaveholder died and in the will he was suppose to return to his family because he was a property.
He filed a case popularly called Dred Scott vs Stanford case in 1857 and it was unsuccessful because the supreme Court ruled against it.
The supreme Court said slavery was legal anywhere and in any states. Slaved have no rights in the Constitution because they are property and not citizen so he as to return to Stanford.