In accordance with Article 6, clause 2 (the "Supremacy Clause") of the US Constitution; pursuant to the "Compulsory Process Clause" and "Confrontation Clause" of the 6th Amendment, to: confront, cross-examine witnesses, and in some cases, compel witnesses to testify; especially a "witness" which:

1. is unable to testify beyond a reasonable doubt as to anything thereby depriving one of one's Constitutionally afforded rights to cross-examine a witness; and
2. based on "law enforcement" [officers'] own determinations1, K9 utilization is fallible and can be corrupted, by administrators/bureaucrats/supervisors and/or handler(s)1 and/or trainers.
3. is likely critical with establishing the possibility of probable cause; and
4. K9's detect not necessarily the [active] presence, rather residual/minuscule amounts that: at some point in time might have existed there, could have came about from another mean(s), or could just be a "false positive"1; and