This page is credited in full to Dave Cushman who created it. His voice is expressed in black colour text and any additions or comments in blue belong to myself. Credit: Dave Cushman’s website.
There are several ways in which we can investigate this property in honey bees.
Pin killing brood in a rosette pattern.
Pin killing brood in a diamond or rhombic pattern.
Whichever pattern is used, pin killing has a serious drawback. The pin leaves a hole, only a small hole, but this renders the comparison with sealed cells invalid. As the aroma leaking through the hole itself will be many times greater than the level of smell that the bees would have to detect if the capping was sound.
Freezing brood using liquid nitrogen is described in the “Minnesota hygiene queen” page in the menu at top left.
Not sure why Steve Taber is not credited with the Nitrogen freezing as he promoted it for many years. See Super Bees by him.