Huw Richards reports from the American Political Studies Association's conference in Chicago.
The United States Supreme Court, guardians of the country's constitution, does respond to external pressures but not those that are often assumed.
Chuck Epp of the University of Indiana said it was widely believed that two external factors set court agendas. The first was the ideological preference of the justices - as early as the 1830s French analyst Alexis de Tocqueville said that "their power is immense but it is power springing from opinion". The second was the political context - illustrated by Finlay Peter Dunne's jibe that "the court follows the election returns".
Dr Epp argues this is not the case. He has looked at the treatment of criminal procedure issues from 1933 to 1990, and women's rights from 1960 to 1990, concentrating on the impact of "landmark" cases.
He found that there was an increase in court activity in both areas following landmark decisions. "For landmark decisions to affect the agenda, there must exist external sources of support that enable potential litigants to bring new cases in response," he said.
His analysis shows that this occurred in both criminal procedure and women's rights - with states increasing their support for criminal defence services in advance of landmark decisions in the early 1960s and the number of women lawyers and women's organisations litigating on rights issues expanding before corresponding decisions in that area in the 1970s.