In the novel The Mirror Crack'd from Side to Side, Jason Rudd was the husband of actress Marina Gregg. She calls him Jinks. He is devoted to his wife. He was unaware that Ella Zielinsky was in love with him until his wife told him.
When Dolly Bantry first sees Jason, she gets the impression that he is the ugliest man she has ever seen. She then notices his eyes, which are "more deeply sunk in his head than any eyes she had seen". The rest of his face is "distinctly craggy, almost ludicrously out of proportion". His nose juts upwards, and he has a big, sad mouth, like a clown. His voice is "unexpectedly pleasant".
On the day of the fête, Jason and his wife receive guests at a private reception upstairs. He pours drinks for some of the guests, including Heather Badcock. He pours Heather a daiquiri, and gives one to his wife as well.
When Inspector Craddock meets Jason, he feels that one would only be able to gauge as much of Jason's thoughts as Jason himself would allow.
Jason tells Craddock about Heather telling Marina the story of how she had met her before in Bermuda. He also mentions that Marina had been slow in replying to Heather, and that he had nudged her gently in the ribs.
He also says that he had been sure all along that his wife was the intended victim. However, he had said nothing, as he did not want his wife to suspect that she had narrowly escaped death.
Later in the novel, Marina complains about her coffee at the studio, saying that something is wrong with it. Jason takes it from her, and pours it down the sink, but secretly keeps some and sends it to be analysed. The analysis finds evidence of arsenic in the coffee.
At the end of the novel, Miss Marple goes to see Jason at Gossington Hall, and he shows her the place where Marina had stood to receive her guests on the day of the fête. Marina had died from an overdose of a sleeping drug, but Jason allows Miss Marple to see her. Miss Marple implies that Jason may hae given her the overdose, and Jason only replies, "She was -- so lovely -- and she had suffered so much."
BBC's Miss Marple
In BBC's 1992 adaptation of the novel, the part of Jason Rudd was played by Barry Newman. Here the secretry Ella Zeilinsky is also in love with him and sends him flowers and notes but Jason brushes off her attentions. Jason is also more involved with Ardwyck Fenn in this adaptation than in the book. He is directing "Elizabeth of Austria" which stars Marina Gregg in the lead role with Ardwyck Fenn as the producer. Jason invited Fenn to the fete and later again to dinner at Gossington Hall--he tells Marina that good relations with Fenn is important to the film project and he really wants Marina to succeed in her comeback. Jason is referred to as "Jay" by most people in this show, especially those in the film studio. He is truly in love with Marina. When Marina drives off for the film studio and gets lost in the country roads, Jason searches for her and finds her. It is implied but not stated explicitly that he poisoned Marina at the end so that she would not need to go through the ordeal of a prosecution. Miss Marple tells him that she is sure that whatever was done was done entirely out of love.
ITV's Agatha Christie's Marple
In ITV's 2010 adaptation of the novel, the part of Jason Rudd is played by Nigel Harman. Here he was the former boyfriend of Lola Brewster. In this adaptation, Jason tells Miss Marple at the end that he put some poison into Marina's cocoa to save her from prosecution. However Miss Marple discovers that Marina did not take the cocoa but had committed suicide in a different way.