The Supreme Court's investigation raises questions about the justices' determination to find the abortion draft leaker

• The Supreme Court could not determine who leaked a draft abortion ruling last May.
• Yet the 20-page report has raised concerns about the rigor of the court's investigation.
• "I'm still disappointed that they didn't find out," one legal expert said.

The Supreme Court on Friday revealed that the justices cooperated in its investigation into a leaked draft ruling of a major abortion case, but weren't asked to speak under oath, following widespread speculation about the scope of the probe. 

"During the course of the investigation, I spoke with each of the Justices, several on multiple occasions," Supreme Court Marshal Gail Curley, who conducted the investigation, said in a statement.

"The Justices actively cooperated in this iterative process, asking questions and answering mine. I followed up on all credible leads, none of which implicated the Justices or their spouses," she added. "On this basis, I did not believe that it was necessary to ask the Justices to sign sworn affidavits."

The 20-page report released by the nation's highest court on Thursday spurred skepticism, given its ambiguity about whether the justices were scrutinized. Investigators perused cell phones and laptops, forensically examined printers, and interviewed 97 of the court's employees, including law clerks, who may have had access to the draft opinion. Yet those individuals went unnamed in the report — and there was no mention that the justices were among them.

Friday's statement appeared to answer that question. Still, the eight-month-long investigation ultimately came up empty, and the leaker's identity remains unknown, raising concerns about the court's determination to finding the leaker. The report also comes amid public discussion that it could have been one of the justices themselves, especially since the court has also come under fire over another alleged breach of a 2014 decision, Burwell v. Hobby Lobby Stores.  A former anti-abortion leader has claimed he had advance knowledge of the ruling, but the author of the opinion, Justice Samuel Alito, has denied the allegations.

"It gives me more assurance than I had yesterday," Carl Tobias, a professor at the University of Richmond School of Law, told Insider. "I'm still disappointed that they didn't find out. Everybody is. So they should keep digging."

The report's inconclusive findings also showed the constraints of a court investigating itself, as opposed to a third party launching an independent probe, court observers said.

"The court did as much as they could given their resources, but the decision to keep this internal prevented them from doing a full blown, thorough investigation," Josh Blackman, a professor at the South Texas College of Law, told Insider.

Had the court been serious about the investigation, "they would've brought the FBI in," Blackman said.

"I think they were committed, but not enough to involve the FBI to actually, really get to the bottom of it," he added.

An executive-branch investigation may have led to the justices speaking under oath, a line the Supreme Court marshal did not cross, according to her statement. But the delicate and fraught nature of the matter could explain why, according to Tobias.

"They're going to be more forthcoming if they're not under oath," he said of the justices. "It would be an insult to them, I think, they would think. To some extent, they're her boss, right?"

The unprecedented leak last May penetrated the often blocked-off world of the Supreme Court, prompting some of the justices to publicly condemn it at the time. The court did so again in an unsigned statement on Thursday, labeling the breach "a grave assault on the judicial process."

The draft opinion, which showed the court was ready to overturn nearly 50 years of constitutionally protected abortion rights, provoked national outrage at an institution that had already been declining in public trust. The leak further eroded that trust, and shattered it within the institution.

And while the report, along with Friday's clarification, offered at least some transparency into the investigation, it failed to restore trust, according to observers.

"There will continue to be suspicions that have bad effects on all interpersonal relations among justices and between justices and clerks and staff," said Richard Pierce, a professor at George Washington University Law School.

Congressional lawmakers have vented about the court's unsuccessful investigation to find the culprit. House Republicans, now in the majority, previously called for their own probe into the leak. Some GOP senators have sounded the alarm about the possibility of future leaks.

"This is inexcusable," Sen. Josh Hawley of Missouri tweeted on Thursday. "And it means brazen attempts like this one to change the Court's decisions - from within - will become more common. Someone ought to resign for this."

But it's uncertain whether new evidence will come to light anytime soon. The Supreme Court's marshal did not note any new leads in her report. While they may be at a dead-end now, some legal experts think that might not be the case forever.

"People like to talk, and so somebody may leak the name of the leaker," Tobias said. "That could happen."