That machine (Danie Krugel) didn't just work on dead people's DNA. It was supposed to use DNA to find the person whether dead or alive. Your DNA sample doesn't change if you are dead or alive.
"It occurred in the British Consulate when the parents wanted a South African ex-policeman to come with a machine supposed to find bodies from hair samples." "Bodies" in this case can be dead or alive.
So if you think it implies the McCanns thought Madeleine was dead at that stage I think that is incorrect.
In short he would appear to claim
he has uniquely developed a handheld device that can find a missing person alive or dead in any given terrain over any elapsed time period.
In debriefing the officers who accompanied Krugel it is possible to hypothesise what he may have been doing and using.
In consultation with a colleague Dr Wolfram Meier-Augenstein we feel he may have been attempting to give the impression he had developed and was using a "Remote Laser based gas sensing device". However his claims regarding the distance of detection, up to 20km and the use of a hair sample are highly unlikely and would be a great innovation in the scientific world. Further provenance of this technique could be sought from Prof. Miles Padgett who is a Professor of optics in physics at the University of Glasgow
http://www.mccannpjfiles.co.uk/PJ/Danie_Krugel.htmFor the families of missing people I believe it is known as 'clutching at straws'.
Krugel advertised himself and posted testimonials from satisfied 'customers' on his blog
https://independentmuse.wordpress.com/2008/09/11/hello-world/ he seemed to be anxious to help people altruistically ... Kate and Gerry who are convinced Madeleine might still be in Portugal
https://www.telegraph.co.uk/news/newstopics/madeleinemccann/12157258/Madeleine-McCann-is-still-in-the-Algarve-claims-mother.html and who were desperate to find her alive and well probably thought Krugel was worth a try ... he was a former detective of South Africa Police's missing children unit after all.
Kate and Gerry had nothing to lose and everything to gain ... absolutely nonsensical to interpret this against them in the way it was. In my opinion a prime example of the prejudice they were and are up against.