In other words, was he pushed or did he jump?
In my opinion he didn't need to resign but he might have been offered early retirement and his pension if he did. The Cipriano fiasco must have been a determining factor in that decision imo since if convicted of perjury his position as a senior officer would have been untenable.
I don't see how he could have taken "early retirement": he was 50 at the time.
According to Article 148 of their regulations (if I'm deciphering it correctly), you can request retirement as of 60 (I haven't found anything about years of service as is the case in some other countries). There is a scheme for those lower down the bread-scale whereby they can get a partial pension, also as of 60, in return for reserve duty, which wouldn't apply in his case, either.
SECÇÃO II Aposentação
Artigo 148.º
Passagem à situação de aposentação
1 - O pessoal de investigação criminal, mesmo quando provido em comissão de serviço em cargos dirigentes, passa à situação de aposentado, se o requerer, quando tenha completado 60 anos de idade.
2 - O disposto no número anterior é aplicável ao pessoal na situação de disponibilidade.
Contém as alterações dos seguintes diplomas:
- DL n.º 235/2005, de 30/12
Consultar versões anteriores deste artigo:
-1ª versão: DL n.º 275-A/2000, de 09/11
http://www.pgdlisboa.pt/leis/lei_mostra_articulado.php?tabela=leis&artigo_id=&nid=35&ficha=101&pagina=&nversao=&so_miolo=I can't find what the penalty is for the most serious category (f - demissão), which in context would seem to mean dismissal.
Assuming the penalty is accordingly more severe, I would imagine that there would be no pension rights, which Amaral does seem to have retained, whether that was actually a full pension or a reduced one as in the equivalent for Europol.
As he already had a fine and a suspension over the Cipriano saga, which I imagine would count as an aggravating factor, then I would find it logical that he either got option D - "inactividade" (one category worse than suspension) or option E - compulsory resignation.
The problem with Option D - "inactividade", is that it doesn't correspond to the "aposentação" for disciplinary reasons cited in the court case.
By elimination, therefore (IMO), my conclusion is that he must have got slapped with Option E - compulsory resignation. Looking through the list of types of misconduct that qualify, the most obvious one (IMO) would be conduct that reflects badly on the PJ's prestige and dignity.