Two approaches - doesn't matter to me which you do - but we need to recognize both URL parameters as representing paid searches: ECID=SEM and ecid=sem.
Either make the string case insensitive - or allow duplicate rules that are case changes of one another.
From Omniture Client Care:
Paid Search detection appears to be case sensitive and the admin console prohibits adding two rules that are essentially different capitializations of one another.
As for setting up duplicate rules that are case changes of one another - this is not a current feature supported in SiteCatalyst as the current admin console is designed to not allow multiple paid search detection rules of the same phrase but different case.