Bulletin: Grits for Breakfast - one of my favourite blogs - sets out its list of the " Top 5 junky forensic sciences" and asks "Why are forensics under fire now?" (Must Read. HL):

Countdown to Wrongful Conviction Day:  Friday, October 2,  2105; 15 days. For information: http://www.aidwyc.org/wcd-2015/

"It's been said that any field with the word "science" appended to its name is "guaranteed thereby not to be a science." With few exceptions, most forensic sciences fall into that category. There are a few hard sciences like toxicology and DNA. But even DNA has subjective elements, we're learning, when lab analysts interpret DNA mixtures. I've found myself explaining to several different folk recently why so many forensic disciplines all of a sudden find themselves questioned, so thought I'd share that spiel with readers. The debate really took hold after 2009, when the National Academy of Sciences issued a major report titled "Strengthening Forensic Science: A Path Forward." That expert review called into question numerous forensic disciplines in a fundamental way, particularly undermining the scientific credentials of comparative forensic disciplines from fingerprints to tool marks. Of the comparative forensics - where somebody sits with a microscope and compares two bullet casings, hair follicles, bite marks, fingerprints, etc. - these are mostly not fields developed through application of the scientific method. Indeed, many of them have little formal scientific underpinning at all. They're just things cops began doing at some point in history (principally post-Arthur Conan Doyle) to accuse people of crimes. No one develops expertise comparing hair follicles under a microscope, for example, unless they're paid by the state to try to match evidence to suspects in criminal cases (though they're not supposed to say "match"). It's not like there's an independent source of expertise defense attorneys can turn to in such instances - nobody does that work except other crime labs, whose analysts were probably all trained at the same FBI schools as the state's expert.  That's not to say that, being unscientific, these comparative disciplines are necessarily invalid. They're just more craft than science. Experienced, expert examiners can tell a lot about the evidence they look at. But it's at root a subjective, not a scientific process, regardless of the trappings. The NAS report laid that history bare. Then there are other disciplines - like arson investigation and diagnoses of "shaken-baby syndrome" - where prior conclusions have been abandoned in light of more recent scientific developments. Texas' new and improved junk science writ makes this state an important site for litigating these issues over the next few years, so expect to hear about these topics more in the future. We're at the front end of an important period when traditional forensics are being reevaluated, in many cases for the first time. Here is Grits' list of top five junky forensic "sciences," all of which are either currently under scrutiny or predictably will be in the near future, with a few dishonorable mentions tacked on since five is awfully short for this list. They're in no particular order and represent my own opinion and no one else's. I could probably even be convinced to drop one or two off the list and add others (make your case in the comments). I offer the following up only as an off-the-cuff thought experiment, not a definitive account. With that said:"  (Click  on the link for Grit's list  - or toss and turn all night in unsatiated curiosity!)
http://gritsforbreakfast.blogspot.ca/2015/09/top-5-junky-forensic-sciences-or-why.html