Who was the chief justice who declared in the dred scott decision that african americans were not citizens?

It's misleading to call Chief Justice Taney a "racist". He wrote the majority decision on Dred Scott. Let it be said that being against slavery in the nineteenth century did not mean a person was not a racist. And, that includes most of the "Western world". Racism existed even among abolitionists. For example, Frederick Douglas and Harriet Beecher Stowe were at odds over the issue of whether freed slaves should be deported to a "new country".

Also, Harriet Beecher Stowe blamed slavery on the entire nation, not just on the South.

For example, by no stretch of the imagination was Delaware, a slave state, in the "South".

At various times in Abraham Lincoln's career, he was against slavery but not necessarily a believer in equal rights for all. That might include his views on Native Americans.