Are American laws different? (SPOILERS)

1.
When Samantha inherits her husbands estate - that is entirely legal - he wasn't that old or mentally incapacitated so Jade could not have claimed undue influence. I think her contest of the will would have failed. That being said - when Samantha dies - how does Jade get the house and everything else back? Surely that would have gone to Samantha's heirs.
2.
How is a murder suspect allowed to return to the crime scene of the murder she is accused of.
3.
How did she get in - Samantha had changed the locks.
4.
How could the arresting detective collude with a murder suspect and visit a potential witness with her.
5.
Wouldn't the boxes in the witnesses house have been inadmissible evidence as they were found without a search warrant.
6.
Maybe the biggest question of all - what was the point of Samantha? Marcus was already married to the heiress - all he had to do was arrange an accident for her father and then kill Jade. He would have inherited everything and not had to share it with anyone.
7.
Was this the longest drawn out attempted murder scene in the history of film? He could have killed her five times over if he had only stopped talking in that unpleasant voice of his.
8.
Was this the fastest dispatch of a villain in the history of film- urghh - he said - and weeks flashed by.
9.
Was this the biggest disappointment in the history of film - Jade and the detective not ending up together? !!!
10
How would the revelation that Samantha targetted Jade's father resulted in the dropping of a murder charge or the invalidation of the will?