Complex sentence: Final title cards inform the audience that Arthur Leigh Allen died in 1992 before he could be questioned further by police, and that a DNA test performed in 2002 did not match a partial DNA sample gathered from one of the Zodiac letters.
Split into simpler sentences: Final title cards inform the audience that Arthur Leigh Allen died in 1992 before he could be questioned further by police. A DNA test performed in 2002 did not match Allen with a partial DNA sample gathered from one of the Zodiac letters.