rock solid, it seems to me, as far as typical criminal trials go.
It is clearly and obviously Hunter Biden's laptop. He signed the original repair ticket. His lawyer called the shop after the FBI got involved asking for Hunter's laptop back. Hunter's lawyer followed that call up with an email request to the shop owner asking for Hunter's laptop back.
https://dailycaller.com/2020/10/18/hunter-biden-laptop-delaware-repair-shop/
Hunter Biden has also not addressed the authenticity of a quote the New York Post produced on Wednesday from the repair show that contains what appears to be his signature, along with his phone number and email address, agreeing to allow the shop to attempt to move data from three Macbook Pros to a store server.
...the computer contained a sticker of the Beau Biden Foundation. Mac Isaac then told Delaware Online that the customer identified himself as Hunter Biden when he arrived at the shop with three liquid-damaged laptops in April 2019
Neither Hunter, nor Joe Biden have denied that it is Hunter's laptop.
Neither Hunter, nor Joe Biden have denied the the emails, pictures or videos are his.
Third parties in Hunter's email chain have verified that the emails are real, one of whom has given his own email address and password to third parties who have been able to go through and authenticate the emails, which are still on the Google server, which have been to and from Hunter Biden.