Excision of skin and tissue (muscle) may be necessary in postmortem investigation of a suspected injection site. Typically a cube of muscle and skin is removed for this purpose. However, it is important to compare the drug concentrations in the suspected injection site with those in a control specimen from the same individual where there is no evidence of injection. Injection sites are not always reliable indicators of drug administration since the presence or absence of drugs in injection site tissue is dependent on the type and depth of the injection. If the injection is made directly into a blood vessel, little drug is likely to remain in the surrounding tissue.