A jury at Chelmsford Crown Court found former builder Paul Taylor, 60, guilty of murder after 23 hours of deliberation.
He was found guilty of three counts of rape, one attempted rape and a serious sexual assault, which were all committed in the months leading up to Miss McGrath's murder.
Mr Justice Owen told Taylor:
"You have finally been brought to justice and you will now serve life in prison."
Taylor is due to be sentenced tomorrow.
For more on this story see the ITV Anglia website.
More top news
Prime Minister Theresa May will be among the mourners at the funeral of Lyra McKee, who was shot dead as she observed rioting in Derry.
Olympic gold medal-winning canoeist Etienne Stott from Nottingham says he doesn't regret his arrest at London's climate change protests.
Coventry City Football Club has announced it is in talks with Wasps over its future at the Ricoh Arena.