Finnish police have the power to impose a fine or arrest you; you're entitled to a interpreter. If you are arrested, you can be detained for three days (longer if the matter is serious) and you should face court within four days.
Police must notify your consulate if you're not a Finnish citizen. You can request they contact a family member or other designated person, but this may be refused if it's considered to jeopardise the investigation. You're presumed innocent until proven guilty.