Martinez is the County Seat of Contra Costa County.
If you mean the video game, contra was a sidee scrolling shooting game for the NES that has been hailed as one the hardest in history, and has the legendary "Konami code"
According to fedstats.gov, the estimated population for Contra Costa County, California, is 1,024,319.
This information is available from the Branch office of the country in question. See link below.
You cannot volunteer for jury duty. Jurors are picked from pool consisting of (depending on the state) registered voters -or- drivers license holders.