The British Psychological Society and Family Justice Council have recently provided a useful document. See BPS&FJC (2). Bond Solon have also provided an interesting survey of expert witnesses. See Expert Witness Survey .
Forensic Health Care are an excellent source of latest news. See http://www.forensic-healthcare.com/ . Bond Solon also provide many news items such as this 2016 review of expert witnesses. See http://www.bondsolon.com/annual-expert-witness-review-2016.aspx .