The narrative around the Mar. 26 sinking of the South Korean Navy Corvette Cheonan, and the death of 46 sailors, seems pretty straightforward: the ship was sunk by a North Korean (DPRK) torpedo. That was the conclusion by a South Korean (ROK) panel of 47 military and military-research experts and three international representatives. The only question left unanswered was the DPRK’s motive, with fallout from an internal power struggle holding the inside track.

But two researchers from the University of Virginia and Johns Hopkins University are suggesting there may have been a rush to judgment, and that the evidence presented by the panel is deeply flawed. Seunghun Lee, a professor of physics at Virginia, and J.J. Suh, an associate professor of Korean Studies at Johns Hopkins, have analyzed the findings of the Joint Civil-Military Investigation Group (JIG) and found them wanting.

The JIG concluded that the Cheonan was ripped in two by an external explosion from a North Korean torpedo, which ROK naval units recovered. But according to Lee and Suh, those conclusions are “riddled with such serious flaws as to render the JIG’s conclusion unsustainable.” They even suggest that some of the X-ray data used to tie the torpedo to the explosion “may have been fabricated.”

Americans who watch television saw a sobering re-creation of the event in which an exploding torpedo’s powerful bubble destroyed a similar sized ship. But according to the two authors, the South Korean Navy has not been able to “produce a bubble simulation consistent with the information presented in the JIG report.” The simulations run by the JIG instead show a bubble forming, striking the ship, deforming the hull, and making a small rupture, not tearing the ship in half.

According to the authors, “If the bottom of the ship was hit by a bubble, it should show a spherical concave deformation resembling the shape of a bubble, as the JIG’s own simulation suggests, but it does not.” Instead, the damage seems more consistent with a “collision with a hard object.”

What is also missing is any sign of what is called the “pre-bubble shock wave,” nor does internal damage and crew casualties appear to be consistent with those inflicted by a shock wave.

Lee and Suh also take issue with the chemical and X-ray analysis of the residue on the hull that the JIG found to be consistent with the chemical signature of an explosion caused by the recovered torpedo. According to the authors, the “critical evidence” used by the JIG “to link the Cheonan sinking to the alleged explosion of the torpedo is scientifically groundless and perhaps fabricated.”

The two researchers also question the torpedo itself, and particularly a blue ink marking on the weapon spelling out “Hangul “in Korean. The torpedo’s deeply corroded surface is consistent with an explosion that would burn off the weapon’s protective paint. The only problem is that ink boils at a much lower point than paint, 150 degrees Celsius and 350 degrees Celsius respectively. “This inconsistency—the high heat tolerant paint was burnt but the low heat tolerant ink was not—cannot be explained and casts serious doubt on the integrity of the torpedo as ‘critical evidence,’” write the two authors.

“While we emphatically note that our findings do not prove that North Korea did not do it, we conclude that the JIG has failed to prove that it did,” the authors argue. “The seriousness of the inconsistencies in fact casts doubt not only on the validity of the JIG conclusions but also on the integrity of its investigation.”

If North Korea didn’t sink the ship, who did? Maybe it was not a “who but a “what.” Some of the damage is consistent with a collision. Is there damage that might indicate an internal explosion? The DPRK certainly has a history of doing provocative things, but part of that reputation comes from the relentless demonization of Pyongyang. The North Koreans have always shown an affection for bombast, but they have been generally careful not to do something that would provoke a war.

It may turn out that the North Koreans did sink the Cheonan, but the evidence is hardly the slam-dunk it has been represented as in the media. And doubts about the DPRK’s guilt may well explain China’s reluctance to join in the pile-on condemnations of Pyongyang, as well as for the careful wording of the recent United Nations resolution that condemned the incident but avoided assigning blame.

What is clear is that in-house investigations are always open to suspicion. No matter what the Israeli’s handpicked panel to investigate the attack on a Turkish ship comes up with, it will have no credibility outside of Israel.

Lee and Suh conclude that “given the inconsistencies” of the JIG investigation, the South Korean government should “re-open the investigation and form a new, and more objective” investigation. “The dead sailors deserve such a report. So does the international community.”

Visit Conn’s blog, Dispatches from the Edge.