Thank you very much for your reply.
I have seen Jeff Marka's page, and if the information he provides is correct the records I am searching for (Courts of Seville and Granada) are - if they still exist - at the Archivo Historico Nacional in Madrid. But without some sort of index it will be almost impossible to find them.
These records I am searching are from the Lopez family I discussed some time ago.
In Portugal, all court case records from the Inquisition (courts of Lisbon, Coimbra, Évora and Goa), some 40,000 in all, are at the Portuguese national archive (Torre do Tombo) in Lisbon. There is a computer index for defendants' names, (and, for part of people especially from the Court of Évora which covered southern Portugal, additional info such as birthplace, parents' names, and so on), avaliable there.
Even a simple name search is very effective (unless the people you are searching for have names that are local versions of "John Doe"). Spelling variations are a problem, since most names have been entered to the index in their modern spelling (a good decision, since spellings changed throughout the centuries, and in the old days there was no uniform spelling for a given name), but some were not, and there are spelling mistakes. I wonder how the first name of one of my ancestors became Rodrigues (a surname) in the index instead of Rodrigo.