Could black people testify in court during Frederick Douglass's time?

Black slaves could
not testify in court.  The reason was that because of their dependent status as slaves, many of
them learned to lie to their master as a way of manipulating him.  So it was thought that the
testimony of someone whose station in life gave him incentive to lie, would not be reliable in
court.  Southern white people were afraid of the example of freedom that a free black presented
to slaves, so they passed laws making freedom for blacks in the South not so much better than
slavery; this would explain why free blacks could not testify in the South.  (I am assuming that
they could not; I think that they could not; you better look it up.)  In the North, there were
no slaves and not a lot of free blacks, but the northern states would not let blacks testify in
court.  The only explanation that I can think of for this is racism.