I have asked many people this question, and not yet got a comprehensive answer: What is psak?
Like, let's say I have a certain piece of food of uncertain status. If I ask my 6 year old kid if it's kosher, and she says yes, and I eat it based on that, obviously I'm an idiot and liable to whatever Heavenly punishment is in order if the food is really not kosher.
On the other hand, if I ask my Rav, and he paskens that it's kosher, I am presumably allowed (perhaps even obligated?) to rely on his psak. But what if he made a mistake, and it's really not kosher? Did I sin in G-d's eyes? Is it considered shogeig (careless) or oneis (accidental)? Do I get timtum halev (spiritual blemish from eating non-kosher)? If he applied the best of his knowledge of Torah, does the Rav get an aveira against his name?
Is there something special about having "semicha" in our times? (I deliberately put it in quotes, since it's not the real semicha.) In other words, if I took the same shaala to a yeshiva student, who's been learning in the Mir for 10 years but never got semicha, and he tells me it's kosher, can I rely on him? Same questions as above for if he's wrong - sin / shogeig / oneis?
Or is it all a matter of personal responsibility: when I have a health problem I consult the expert: my doctor. When I want financial advice, I go to a financial consultant. And when I need spiritual advice, I go to my Rabbi or local talmid chacham for expert opinion. The "semicha" that my Rebbe has is then kind of like the Med School certificate on the doctor's wall: accreditation from a recognized 3rd party that this person knows what he's doing, and I can rely on him, if I trust the certifying authority. It's helpful to have semicha, but if I have personal knowledge that my friend from the Mir knows his halacha, I can rely on him as much as a Rabbi with "semicha".
So, what is the correct explanation?