It wasn't a technicality. A key part of the "overwhelming" evidence was the testimony of one guy, and a lot turned on whether that one guy was telling the truth. Turns out that one guy told the investigators a totally different story when they first interviewed him. That raises a substantive issue about his credibility and the credibility of the evidence he gave, not just a technical issue about whether some evidence was obtained in the right way.
The issue conservatives often complain about (actually it isn't just conservatives, just about everyone outside of the US thinks that this is an absolutely mental feature of the US legal system) is the exclusion of evidence that was obtained improperly regardless of whether the impropriety affects the credibility of the evidence.
For example, a murderer can say "Yes I killed her, and her head is in my fridge", the cops can then go and find the head in the guys fridge, only to see the freely given confession and conclusive physical evidence thrown out because someone forgot to tell the killer he was entitled to speak to a lawyer.
In other words, even if there is no doubt about the reliability of evidence, and even if the evidence is conclusive, US courts will sometimes throw out that perfectly good evidence just because someone didn't follow the correct procedures when they obtained it. That is what conservatives mean when they complain about someone getting off "on a technicality".