I am still waiting for someone to point out to me the relevant article in the penal code that private attempts to provide the PJ with information that may assist the investigation are illegal, per se.
Why?
Are you asking about a situation where I go to the PJ to volunteer information that has come to my attention and is relevant to the investigation? If I know a crime has been perpetrated, should I not report it?
The thread topic is conducting a private criminal investigation in Portugal, and the info in Kate's book that this is illegal.
If anyone can come up with a private investigation in Portugal known to the police, then the question would be answered.
Sifting through the entire penal code, translating it accurately, analysing the result, merely to work out if such an investigation is explicitly prohibited or instead effectively prohibited by a collection of combined articles sounds like an arduous task for very limited reward.