Upheld but with limits:

https://en.wikipedia.org/wiki/Austin_v._United_States

This was the push that got the snowball rolling, so to speak.

The courts have evaluated civil forfeiture under

4th amendment arguments

5th amendment arguments

6th amendment arguments

8th amendment arguments

14th amendment arguments

and only found the 8th amendment argument against excessive fines to hold some weight, but not to undo civil asset forfeiture but only clarifying that the 8th amendment actually applies to the states

They file the case against the property, not the human. If we want a constitutional guarantee on the property then we need a new constitution with its own property based bill of rights

the cases aren't on my clipboard but anyone passing by feel free to fill them in. The 8th amendment case was before the US Supreme Court this year or last, despite the positive ruling it did not get the man's property back until the state he was in re-ruled.

If property doesn't have rights, how can the 8th ammendment protect it, yet it doesn't have protections under the others? The 4th explicitly requires the seizure of property to be based on at least probable cause. Just seems like a massive contradiction.

I guess someone needs to file a civil rights suit because they were deprived of that property under the color of law. The 4th ammendment is quite clear that one is to be secure in their affects. Doesn't matter if the case was filed against the property, the effect was felt by the person.

For a layperson like me, can you help me understand how it is that a case can be filed against property with respect to civil forfeiture while ignoring the constitutional violations against the person? I mean, how can anyone with a straight face claim that seizing property does not have burdensome negative consequences directly against the property owner, a real person who does have constitutional protections? How is it that the law in practice can become so far away removed from what seems so obviously wrong to those of us not familiar?

I trust you that there probably are many court decisions that have found civil forfeiture not to be unconstitutional. But it feels like it comes down to some pedantic twisting of words which go against the spirit of the constitution.

It is paradoxical. The reality is that many constitutions around the world have aspects that contradict and can overrule other rights afforded in them, and America is no exception despite the advertisement to the contrary.

In this case because the human is not on trial, they don't get to exercise those rights.