Kelly is crime scene investigator. She is examining a stain that she suspects is blood. Presumptive tests indicate blood, so she is choosing which confirmatory test to use. What are the disadvantages of confirmatory tests? Kelly considers using the test to confirm whether the stain is blood; however, she knows that it could be unreliable because the stain is on a leather boot. Kelly considers using the test, but she believes the stain may be about 35 years old, and this test is not as reliable for stains over 20 years.