A Union County man was sentenced to 40 years in state prison Wednesday for the strangling death of his 19-year-old girlfriend in 2020, authorities announced Friday. Bryan Gonzalez Martines, 24, of Plainfield, was found guilty by a jury in July 2023 of first-degree murder in the July 6, 2020 killing of Brenda Montoya-Cruz, who had reported just a week before her death that her boyfriend had threatened and attacked her. Gonzalez Martines initially eluded police by jumping from a second story roof of an apartment building on Kensington Avenue in Plainfield when police arrived for a wellness check…