They tested a piece that had been seared in a fire and had been repaired.
No, it had not been seared by the fire, Ann. This was a corner that had been frayed, cut away, and patched. It was actually quite some distance from the fire damaged portion of the Shroud. Merely searing carbon does not change the Carbon in a sample doesn't change the ratio of C-14 to C-12 and C-15 in the sample. Searing is a chemical change, not a nuclear change. ADDING contaminants, like a more patch, changes that mix.