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For now I think we have enough information without further analysis. The analysis is not scientific proof as the police are presenting it. Its a new technology and is not admissible in to a court of law (in the USA anyway). Importantly what could be analysied as a 'clean' transaction one year ago could now be seen as linked to an illegal website as links can be changed at any time.
Due to the complexity of this issue and how wallets/addresses work within the bitcoin network,
and due to the ignorance of the court system on how the Bitcoin system actually functions,
it would be in your interest to get a "expert" in Bitcoin to write a certification on your behalf to
explain what is and is not possible with the Bitcoin network. Maybe also hire someone to testify
in your trial.
In theory, your statement about links not being linked till a year later is correct, but the site could be
subpoenaed to answer when the site added it and it could have been added years in the past.
Meaning that at the time, the site could have had that information when you performed the buy/sell.
(You still have no legal requirement (that I am aware of) to check all incoming bitcoin txs origins.)
It is important to have expert testimony on your behalf at trial, so that the prosecution does not misconstrued or
outright make up what can or can not be done or how the system works. You will need an expert to dispute their
misunderstandings and unreasonable expectations.
This is just my personal opinion and should not be considered legal advice.