Complex sentence: The analysts took from the items used in the test six different DNA samples, all of which turned out to be identical, but they differed substantially from the blood sample examined in 1996, the authenticity of which was therefore questioned.
Split into simpler sentences: The analysts took from the items used in the test six different DNA samples, all of which turned out to be identical. They differed substantially, however, from the blood sample examined in 1996, the authenticity of which was therefore questioned.