ELF – Engelsk läsförståelse (HPHOST2015P4)

In the following text there are gaps which indicate that something has been left out. Look at the four alternatives that correspond to each gap and decide which one best fits the gap. Then mark your choice on your answer sheet.

Which Pills Work?

Physicians have 1_____ vitamin D supplements to their patients for a decade, with good reason: dozens of studies have shown a correlation between high intake of vitamin D – far higher than most people would get in a typical diet and from exposure to the sun – and lower rates of chronic diseases, such as cancer and type 1 diabetes. So when the Institute of Medicine, which advises the government on health policy, concluded in November that vitamin D supplements were unnecessary for most Americans and 2_____ harmful, patients were understandably confused.

The issue exposes a rift among experts over what constitutes valid proof when it 3_____ nutrition and could affect medical advice on many other supplements. On the one hand are scientists who insist that the only acceptable standard is the randomized clinical trial, which often compares the effects of a medical intervention, such as high intake of vitamin D, with those of a placebo. The scientists who reviewed the vitamin D findings fall heavily into this camp. On the other hand is the institute panel which discarded a raft of observational studies, in which researchers compare the health of populations who take vitamin D supplements with those who do not. In theory, such epidemiological studies are 4_____ to clinical studies because they rely on observations out in the real world, where it is impossible to control for the variables scientists seek to understand. Researchers compensate for the lack of control by using large sample sizes – some vitamin D studies track 50,000 people – and applying statistical techniques. According to these studies, high levels of vitamin D are generally beneficial.

In the aftermath of the institute report, some physicians are now taking potshots at clinical studies. In nutrition, they say, true placebo groups are hard to maintain —how do you prevent people in a control group from, say, picking up extra vitamin D from sunlight and food, which can lead to the vitamin’s 5_____? It is also tough to single out the effect of one vitamin or mineral from others, because many work in tandem.

Scientific American

Forensic Evidence

Thanks to TV programmes like CSI: Crime Scene Investigation, forensics is perceived as a glamorous science. In reality, of course, it is anything but, and in some cases it isn’t particularly scientific either. Fingerprints, tool marks and similar evidence can be invaluable in bringing a criminal to justice. The problem is that expert witnesses have tended to exaggerate what forensic techniques can tell us.

Forensic science has to transform itself. For a role model it could look to DNA analysis, with its careful attention to what the evidence can and cannot tell us. There are signs a change is already under way, but it is not happening fast enough. The big obstacle is the courts. Expert witnesses command great authority in the eyes of jurors and judges, and problems arise when the so-called experts claim greater precision for their techniques than they can support.

In the US, some courts have adopted screening mechanisms to try to prevent untrustworthy experts from testifying, but this is a problem when judges without extensive scientific training have to decide whether practitioners know what they are talking about. Courts have traditionally deferred to “the scientific community” to help them distinguish respected practitioners from charlatans. However, in some forensic sciences, many of the practitioners are not scientists.

This was the difficulty faced by the Supreme Judicial Court of Massachusetts in a recent murder trial. The point at issue was the reliability of fingerprint identification. The state argued that, since all fingerprint examiners believe fingerprint examination is fail-safe, the court should back it. The defendant argued that a broad cross-section of scientists and scholars who had studied the issue agreed that the reliability of fingerprinting will never be known until its accuracy is measured – something that has yet to be done.

The court backed the practitioners. It ruled that, in order to be admissible evidence, fingerprinting needed to be accepted only among practising fingerprint examiners. This was a victory for the state, and a defeat for science. According to the courts logic, any community of practitioners is now entitled to assess its own reliability.

This is unfortunate because many forensic disciplines appear ill equipped or disinclined to take a rigorous empirical approach. A century of fingerprint practice went by before the first attempt to measure its accuracy was published. The FBI recently laid out an ambitious research agenda to place fingerprinting on a more scientific footing, but only after it was forced to admit that a false fingerprint identification had wrongly implicated an Oregon lawyer in the Madrid train bombings of 2004.

A good illustration of the lack of research underpinning much forensic science is the use by the FBI of an esoteric technique called comparative bullet lead analysis (CBLA), which rested on untested assumptions about the diversity of lead sources and their chemical consistency. The validity of these assumptions was only addressed in the 1990s. In 2004, the FBI discontinued CBLA after a critical report from the National Research Council (NRC).

What does this say about the state of forensic science? At a National Academy of Sciences colloquium, Ronald Singer, former president of the American Academy of Forensic Sciences, said the CBLA episode showed forensic science was “self-correcting”. That is a generous interpretation, considering that it took more than 30 years for the FBI to fund the NRC report.

Here’s another way of viewing it: the FBI’s use of CBLA turned the usual relationship between law and science on its head. Rather than performing scientific research to determine what can responsibly be said about a form of evidence, and then offering such testimony in court, it appears the FBI testified first and did the science later.

Change is coming. Scientists from many disciplines are taking an interest in forensic science. But unless the courts stop rewarding practitioners for ignoring science, the revolution is likely to take longer than it should.

Simon A. Cole, New Scientist