Regina Regina:
Yes it would. How could it not be an attempt to obstruct.......not to mention threats made. Bikers gangs try it all the time and it's illegal.
Because taking part in a legally obligated action as part of a judicial proceeding is by definition helpful to the judicial proceeding.
$1:
You can't make the spouse tell the truth
Just to come back to this point. Yes clearly physically you can not force someone to tell the truth. However legally obligate someone to do so, and as part of any reasonable law it must include punishment for non compliance.
What it seems like you are suggesting is that any non voluntary testimony is an obstruction of justice. It would cause a total breakdown of the system of witnesses. A friendly witness on one side could just refuse to answer questions on a cross examination. The police would never say anything other than whatever story they worked up with the prosecution.
Unless I have somehow failed to understand your point, I just can't see how laws that prohibit lying could be viewed as equal to a criminal organization threatening a witness.
An act which is a crime even if the person being threatened isn't a witness.
Taken to the next level all laws that carry punishment could be classed as uttering threats.