Generally, there are two types of forensic validation: developmental and internal. In the context of probabilistic genotyping (PG) software, developmental validation is undertaken by the software developers and involves the demonstration of the verification of the functionality of the system, the accuracy of statistical calculations and other results, the appropriateness of analytical and statistical parameters, and the determination of the limits of the software. Internal or end-user validation is undertaken by the laboratory. It is the accumulation of test data within the laboratory to demonstrate that the software is performing as expected.

Within this chapter, we describe the requirements for the internal validation of PG software. We show examples of the expected results for a number of the requirements for the continuous PG software STRmix.