Using primary
sources makes it difficult to ensure that you haven't
missed something. When using secondary sources you simply have to
determine what bias exists in the source, and if there is no
significant bias (for example, it's an independent newspaper article
about the case), you can trust that nothing significant has been
missed out.
!!! The suggestion that newspaper articles are unbiased is a novel one.
The word "significant" is significant. Newspapers usually have quite
general biases towards certain political POVs, they don't usually have
a bias towards a particular side in a civil law suit.