Obstruction vs. Interference at First Base...how do you know which?

Question

I'm an umpire, and I've been trying to understand how obstruction/interference works at fist base exactly. For example, the throw from the third baseman takes the first baseman into the basepath- is this obstruction of the runner, or does he have the right to field the throw? Or, if the runner knocks into the fielder while fielding the throw, is that offensive interference? Some ppl have told me it's the "umpire's judgement"- if that's the case, what should be the deciding factor?

Answer 1

its a judgement call by you if you think the runner could of got back beforeh te feilder made a play.

It an be obustrion intrefernce is blocking  a base without a ball if its not coming to him. Its hard to make a call like that.

If you work with another umpire ask him talk to him.

Answer 2

if the throw take the first baseman into the base path he has the right to field it  and if the runner purposely knocks into the first baseman it is offensive interference