IIRC, from Portuguese media reports, SY requested DNA samples from "suspects" and this was denied by the judge. With this refusal by the judge, SY allegedly wanted to obtain DNA by underhanded methods without the knowledge or consent of the persons involved which is manifestly illegal here in Portugal.
I did read about an investigation of a gang member in Porto. The judge of the criminal court authorised taking the sample from the suspect who then refused to give it. After his refusal, another court authorised the obtaining of the DNA sample by "force", that is from a cigarette or a piece of chewing gum, etc. The point I'm making is that the obtaining of the DNA must first be authorised by a judge and then the person signs a consent form.
BTW, regarding this case of the gang member, Marinho Pinto, in the newspaper article, argued that making someone give their DNA against their will could be considered self incriminating, thus against the constitution.
If, as davel, has stated, people having given their DNA samples voluntarily, I suppose that these persons have nothing to hide or fear.