Bill Jackson was the social worker at Wentworth in the very beginning of the series, appearing from Episodes 002 - 004.
Time At Wentworth
Bill was quite devoted to his job, much the same as his wife Meg Jackson. This annoyed their only son Marty who felt that both his parents spent too much time devoted to the prison. One day Marty turned up at the prison to talk to his father, but Bill was too busy and sent Meg out to see him instead.
Being one of three male staff at the time (though technically Eddie Cook was contracted to work there), Bill was often sought after by some of the women, especially Chrissie Latham, who openly came onto him, kissing him moments before Meg entered his office. Bill was uninterested in Chrissie of course, being a married man.
When the Franky Doyle Riot took place, Bill learned that Meg was being held hostage, and had to be physically restrained when he tried to make a grab for her when the gates were opened to let out a pregnant prisoner (Rosie Hudson). Bill eventually agreed to tesitfy in Franky's favour in order to end the riot.
It is also revealed that he wanted to resign from Wentworth for a long time, and so did Meg.
Death
As the riot ends, some of the women make a final attempt to fight. In the scuffle, Lynn Warner screams she was the first to see when Bill Jackson is stabbed with a pair of scissors, it pierced his lung. He dies on the way to hospital, with Meg accompanying him. The culprit is later revealed to be Chrissie Latham.