I think any dog is capable of biting, but breed traits and situation are huge factors.
I have two small dogs, so not the kind that could kill an adult, but could theoretically really hurt a child.
I am very familiar with my dogs, their body language and what will trigger their fear/anxiety, so I would have different levels of relaxation/vigilance depending on the situation.
For me, DH and our friends & family who know them (adults) the dogs will be calm and relaxed. If they are unhappy with a situation (for example, nail cutting) they will demonstrate clear warning signals well before they would show any aggression. An adult familiar with dogs would be easily able to read this and back off. Backing off would deescalate the situation immediately.
With DD (baby), they are familiar with her and far more relaxed than around children they don't know, but I'm always watchful of their interactions. I will intervene at the slightest hint of the dogs being uncomfortable, well before they start giving warning grumbles.
With children other than my own, or adults not familiar with dogs, I am hyper vigilant. I monitor their interactions very closely, and know from my dog's body language if they're not comfortable/get them out of the situation immediately.
I don't believe my dogs would ever hurt