Ethics are certain laws which guide our lives. Just like there are ethics that govern various day to day activities we indulge in like driving, respecting people, justice for individuals, there are ethics for research and particularly medical research.
The aspects included under medical research are very broad and not specified to meet every requirement for research- which is why one finds many instances where research is able to find loopholes through which it can fall out and become unethical.
The basic tenets of medical research are justice, beneficence and autonomy. Using these broad outlines, we can judge each individual research and find out how ethical it is.
Under justice come equal participation and equal treatment for all participants; under beneficence, comes doing good that is benefit over risk and under autonomy helps the participants decide on whether to agree to participate in the research( consent).
Usually decisions of ethics in medicine are taken by boards called the Institutional Review Boards, which are constituted by scientific members, non scientific members, lay persons and sometimes legal experts/ethicist/ religious scholars.
Below are three sources for guidelines set forth by various international organisations.
National organisations are listed at this site: