THE defense in Phil Spector’s murder trial has been trying to paint Lana Clarkson as depressed and even suicidal - but one of the blond actress’s last let ters to a friend suggests otherwise. In her new book, “Secrets Can Be Murder, What America’s Most Sensational Crimes Tell Us About Our selves,” former Channel 2 News anchor Jane Velez-Mitchell bares portions of a never-befo re-seen letter Clarkson wrote to a pal one month before she was shot dead at the ...