Here are some tips:
First of all, look at the appearance – the berries should be dry and whole.
Fresh blueberries have a light whitish waxy coating. If it is not there, the berries may have been lying around for a long time or have been transported incorrectly.
The berries should be easy to pour into the container. If they are shrivelled, stuck together, and leaking juice, it is better not to pick them.