The Supreme Court appeared resistant Wednesday to increasing constitutional safeguards against the use of some eyewitness testimony at criminal trials, despite mounting evidence that eyewitness identification plays a crucial role in cases in which people were wrongly convicted.

The justices heard arguments in a case that deals with a narrow slice of the issue of eyewitness identification.

Judges already can bar testimony when the police do something to influence a witness to identify a suspect. In a case from New Hampshire, a man who was convicted of theft based on eyewitness testimony wants the court to extend the power of judges to exclude testimony when identifications are made under any suggestive circumstances, even when the police are not involved.

But taking the police out of the picture raised many questions among the justices across the bench.

Justice Antonin Scalia asked, "Why is unreliable eyewitness identification any different from unreliable anything else? So shouldn't we look at every instance of evidence introduced in criminal cases to see if it was reliable or not?"

Justice Ruth Bader Ginsburg peppered Richard Guerriero, the public defender representing Barion Perry at the Supreme Court, with questions about why the court should add to existing protections that include the ability to cross-examine a witness and ask the judge to tell jurors about problems with eyewitness identification.