Police are hoping that DNA testing may link a man they picked up in Harlem this weekend to the series of rapes that have occurred throughout Hamilton Heights over the last month. A Pennsylvania ex-con was picked up Saturday for questioning and is being held on an outstanding warrant as they await to see if his DNA matches a sample recovered from a discarded soda can during one of the four sexual assault incidents in Upper Manhattan. When the man was picked up over the weekend, he told cops, "If you're looking at me for something, I have a twin brother." (He doesn't.) But three of the four victims who have made it down to Special Victims Unit have failed to pick the suspect out of a lineup. Yesterday the Guardian Angels led a rally to continue to spread the word about the rapist. Assemblyman Keith Wright said, "This community will not rest until this person is arrested, indicted, convicted, and incarcerated." Wright is proposing $100,000 in state funds be made available for increased street lighting in the neighborhood.