This 'bias' is not necessarily inappropriate because of the inherent asymmetries of DNA evidence - it is statistically more powerful for exoneration than conviction. This is because of the False Positive Problem (similar to the Birthday Problem in probability): if the actual incidence of a phenomenon is lower than the false positive rate of the test, a positive result is likely erroneous even on a highly accurate test.
This is why a strong prior, developed through traditional policework, is necessary to increase the reliability of DNA results - most results obtained through database trawling will be false - and these will be numerous if the database is large enough. It is also part of the reason why exonerations are more robust than identifications.
This particular case may not suffer from these statistical problems, but they are worth keeping in mind, as it sets a precedent.
That isn't bias but rather an understanding of burden of proof. If you think it is, then you are very fundamentally misinformed about how our society functions.
Careful, your bias is showing..