Police Commissioner Tyrone Griffith said Wednesday said there is no clear evidence at this point of a serial killer targeting sex workers in The City, following the gruesome slaying of a Jamaican woman, reputed to be a sex worker.Detectives were seeking to determine whether there are any patterns that might link her death to a rash of similar attacks on women who ply their trade at night on City streets – all between the months of July and September.But an expert on human trafficking has warned that numerous non-national women, particularly from Jamaica, are vulnerable to gross acts of violence because of their fragile economic situation.