Despite calls for reform to enhance forensic science, insufficient attention has been paid to the potential errors arising from exclusions. Often based on intuitive judgment rather than empirical evidence, exclusions can lead to significant errors. Additionally, exclusions can imply inclusions, especially when ancillary information narrows the pool of suspects in an investigation. Without empirical evidence demonstrating that class characteristics alone can consistently be used for comparison with high repeatability, replicability, and accuracy, these characteristics should not be employed for exclusions. Errors in exclusions require the same scrutiny as errors in inclusions. Validity studies and reports of the accuracy of a forensic method must include both false positive rates and false negative rates, since only focusing on false positive rates can lead, and has led, to errors and subsequent miscarriages of justice.