Just to add - Kate also had the "smell of death" on her own things, so what does she know about O'Brian?
Did he find Maddie dead from a fall and told the parents later, perhaps?
Gosh . . .
A person's belongings can have a smell of death on them without that person necessarily having been in contact with the dead body. This can happen if anyone else brought the scent to your belongings. Say, someone wants to get rid of a body and wraps the body in YOUR clothes. Or, say, someone wants to frame you and rubs your stuff on the dead body before removing it.
Instead of viewing Kate's wacky-sounding statements through the lens of "she's guilty", it can be informative to try viewing them through a lens of "she's innocent". Not as a Kate apologist, but as a sleuth. If someone says to you that your child's toy smells of death, and you are innocent and have absolutely no clue how that could be, what would you say?
Also, a few more interesting points:
* Kate and Gerry were interviewed *separately* by the PJ. If one or the other wanted to plant some juicy suspicions in the minds of the police, it would be easy. "Kate had been very stressed out by the kids during that time, and yes I'm so sorry to say it, but did see her slap Madeleine once. I was worried about her sanity, to be truthful."
* If you did a bad thing and are lieing about it, wouldn't it be pretty easy to account for FIVE MINUTES of your time? Make up anything! Five minutes is easy to fill with search for your lost child. I daresey a really good liar could also easily fill up the FIFTEEN MINUTES that Gerry has unaccounted for that evening, between 9:05 (precisely) when he left the table and 9:20 when he started up a chat with Jeremy Wilkins.
* If you're innocent and telling the truth, and you were in shock and fear at the time and are in shock and misery now, you might very well admit that there's a large zone of mental numbness during which you frankly have no idea where you were or what you were doing.
It's all about character, folks.