Casting 2.3 - Falls of the Reichenbach

Kitty Riley : Katherine Parkinson - IMDB page

An ambitious journalist, Kitty is looking for a scoop, and ready to confront Sherlock for that. The first meeting turns to an humiliation, Sherlock being haughty and contemptuous. But Moriarty decides to use her as an asset, and she will play a good part in Sherlock's fall.

Ella, Psychotherapist : Tanya Moodie - IMDB page

John's therapist; he came after his return from Afghanistan, but Sherlock, as a provider of action and adrenalin, proved to be much more efficient than a therapy, and John stopped the appointments. When his best friend dies, he needs to resume it.

Chief Superintendant : Tony Pitts - IMDB page

He doesn't understand why Lestrade is so trusting and accommodating with Sherlock. Donovan and Anderson's suspicions seems much more justified. After all, if Sherlock is not a psychopath, he is, for sure, a "weirdo". Something the Chief Supertintendant should not have said before John, for the sake of his nose...

Judge : Malcolm Rennie - IMDB page

It' s probably because he is a seasoned judge that he got the trial of Moriarty to run. Not a gift at all... Intelligent and  blessed with a strong character, the judge has no other option than accept the "non-guilty" verdict. Moriarty made sure the jury would ask for it.

Moriarty's defence barrister : Ian Hallard - IMDB page

This lawyer is as young as the judge is seasoned, but Moriarty needs no one to defend himself. He will call for no witness, will say nothing. Blackmailing members of the jury is much more efficient. 

A small role, but Mark Gatiss seized this opportunity to stage a scene with his real-life partner.

2.3 Falls of the Reichenbach

John has resumed his appointments with his therapist. A new trauma occurred : Sherlock died.

Casting 2.2 - the hounds of Baskerville

Henry Knight : Russel Tovey - IMDB page

Orphan at ten, witness of the murder of his father, Henry succeeded in building his life. He is still seeing a therapist, though. But as memories are coming back, new events make him feels weak and insane.

2.2 The Hounds of Baskerville

Synopsis:

Sherlock is starving for a case, when a young man arrives : 20 years ago, he saw his father die, killed by a monster, a "gigantic hound", as far as he can recall. Now, the monster may have come back, where all happened, in Baskerville. But there is a high-security military base nearby, performing genetic experiments, which could have a responsibility in this mystery.

Casting 2.1 A scandal in Belgravia

First of all, "The woman" :

2.1 A scandal in Belgravia

Her Majesty, regular reader of John's blog, request Sherlock's discreet intervention in a very delicate matter.

A woman, called Irene Adler, could compromize a member of the royal family.

Although not especially interested in the royal affair, Sherlock is requested to accept it. But the woman he is about to meet is all but common.