Jim Atwood is the husband of Cath Atwood. He is one of the prime suspects in the rape of Trish Winterman as well as two other women.
He owns a garage in Broadchurch and works there as a car mechanic. According to his wife, his garage is not doing well.
Jim is a suspect in the Winterman case, becasue his DNA came up as a match on Trish's sample. His wife also finds condoms in his car that match the brand that the rapists used. Cath also confirms that he'd have been able to rape the other two women, since she had been away on both occasions.
His wife kicks him out of their home due to his infidelity and her suspicion that he had raped Trish.
Later, we learn that he and Trish slept together on Saturday morning, which explains the DNA match. The reason he had brought condoms was to sleep with one of the young waitresses who were serving at his wife's 50th brithday party.