Scientific misconduct is the violation of the standard codes of scholarly conduct and ethical behavior in professional scientific research.
A Lancet review on Handling of Scientific Misconduct in Scandinavian countries provides the following sample definitions:
Danish definition: "Intention or gross negligence leading to fabrication of the scientific message or a false credit or emphasis given to a scientist"
Swedish definition: "Intention[al] distortion of the research process by fabrication of data, text, hypothesis, or methods from another researcher's manuscript form or publication; or distortion of the research process in other ways."
The consequences of scientific misconduct can be damaging for both perpetrators and any individual who exposes it.
In addition there are public health implications attached to the promotion of medical or other interventions based on dubious research findings.
Motivators for scientists to commit misconduct:
Career pressure Science is still a very strongly career-driven discipline.
Scientists depend on a good reputation to receive ongoing support and funding, and a good reputation relies largely on the publication of high-profile scientific papers.
Hence, there is a strong imperative to "publish or perish."
Clearly, this may motivate desperate (or fame-hungry) scientists to fabricate results.
Ease of fabrication In many scientific fields, results are often difficult to reproduce accurately, being obscured by noise, artifacts, and other extraneous data.
That means that even if a scientist does falsify data, they can expect to get away with it -- or at least claim innocence if their results conflict with others in the same field.
There are no "scientific police" who are trained to fight scientific crimes; all investigations are made by experts in science but amateurs in dealing with criminals.
It is relatively easy to cheat although difficult to know exactly how many scientists fabricate data.