Complex sentence: The 1 in 200 million match probability calculation did not allow for the fact that the perpetrator might be a close relative of the defendant-an important point, since the defendant had a half-brother in his 20s whose DNA was never tested.
Split into simpler sentences: The 1 in 200 million match probability calculation did not allow for the fact that the true perpetrator might be a close relative of the defendant. The defendant had a half-brother in his 20s whose DNA was never tested.