Short answer
You are not obliged to go, you are not obliged to answer, and you may always speak to a lawyer first. Call before you respond to the invitation — not afterwards.
There is a letter on the doormat, or you get a call from a detective: could you drop by for a chat. No officers at the door, no handcuffs. That sounds reassuring, and that is exactly where the risk lies. An invitation for a police interview is not a no-obligation cup of coffee — everything you say goes down on paper and stays in the case file, even if you say something different later.
Below is what an invitation actually means, what you should and should not do, and what happens on the day itself — from the front desk to the signature at the bottom of the police report.
1 — You are a suspect, even if it does not say so
An invitation for a police interview almost always goes to someone who has been designated as a suspect. The letter often states no more than an article number and a date. Look that number up, or have it looked up: the difference between art. 300 Sr (mishandeling — assault causing bodily harm) and art. 302 Sr (zware mishandeling — grievous bodily harm) is the difference between a community sentence (taakstraf) and a prison sentence.