Adoption records, consistorial (family) actions, and materials relating to criminal trials are closed for 100 years for data protection reasons. Other sheriff court papers are open to the public.
Certain series are searchable, such as the registers of testaments up to 1925, which have been digitally imaged and are available through the ScotlandsPeople website as well as in the NRS search rooms. (There is a guide to wills and testaments which gives more information on using the records). Post-1860 civil actions are gradually being individually listed as part of a recataloguing programme. Searching other court records can be frustrating because most remain unindexed.
There can be large gaps within individual series, particularly for earlier periods. Additionally, sometimes a particular type of record (such as the ejection of tenants from estates) is logged in a special register at a later date, but lumped in with other types of records for earlier years. There can also be a degree of overlap with Court of Session cases, for example in the records of people appointed to handle the affairs of lunatics and minors.
Some sheriff courts have now closed and their functions were absorbed by neighbouring courts. If no trace of a case is initially found, bear in mind that the jurisdictions of sheriff courts varied at different periods, eg the overlap of the boundaries of the Argyll and Inverness-shire sheriff courts at Fort William (NRS reference SC28 and SC52).