Convicted by Code: Defendants should be able to inspect code used in forensics
This defense attorney was creative for asking to examine the source code, but that isn't the only way to cast doubt on the accuracy of the software that DNA matched his client to the crime scene.  He could simply obtain a copy of it and have an expert run tests to determine a false positive rate and also what types of scenarios cause the software to deliver false positives, then call that expert as a witness.