I read of this a couple decades ago. It was not merely that respiration was detected, but that the rate of respiration was connected to the circadian rhythm, which was not explainable otherwise.

I remember reading that every single "Is there life?" test they've sent to Mars has come back positive, but then someone always comes up with some bullshit excuse as to why they need to throw the tests out.

This type of "evidence" needs to be replicated to make sure it's not a false reading. This will happen over time. No one wants to be the guy to proclaim life existed on Mars without strong proof.