The US law enforcement authorities are regularly guilty of irregularities during investigations and lawsuits, the authors of a report released Tuesday said.
Police in the United States has been under fire in recent months over racism and the use of excessive force.
Scientists examined the files of nearly 2,500 people who had been acquitted after wrongly convicted over the past 30 years.
In doing so, the researchers found that illegal or unethical behaviour by police officers, as well as prosecutors, had contributed to more than half of these miscarriages of justice.
The most common mistake is the concealment of exculpatory evidence, which is found in 61 percent of false murder convictions.
Pressuring witnesses, false testimony during trials and submitting drugs to suspects and then arresting them are also common in the report, a project of the universities of California and Michigan.
As with the use of excessive force, black Americans are more likely to be victims of such abuses than white suspects. This is especially the case in murder or drug cases, the report says.
The abuses have little effect on the guilty police officers and prosecutors. Only 17 percent of cases leading to miscarriage of justice resulted in sanctions.
However, the consequences for the victims are significant. Those wrongfully convicted of murder spent an average of 13.9 years in prison before being acquitted.