The attorney told DailyMail.com that one alleged recovery, recounted to him by a supposed crash retrieval program insider, involved a 30ft saucer partially embedded in the earth, with some fantastical properties.
'They tried to hook a bulldozer to it to pull it out. And it pulled out a shape like a pie slice, almost like it was part of the way it was constructed,' Sheehan said.
'When it came loose a couple feet, they stopped immediately. They didn't want to destroy the integrity of the machine.
'They had a guy go into it. He got in there, and it was as big as a football stadium. It was freaking him out and started making him feel nauseous, he was so disoriented because it was so gigantic inside.
'It was the size of a football stadium, while the outside was only about 30 feet in diameter.'
Sheehan said that space was not the only warped dimension around the craft.
'He staggered back out after being in there a couple of minutes, and outside it was four hours later,' he said. 'There was all kinds of time distortion and space distortion.'
Physicists have theorized that propulsion of an advanced craft could theoretically involve warping space-time around it to negate the effects of gravity.
But Sheehan declined to give further details – including a location and date of the incident – and said he was unable to provide evidence for the claims.
The lack of details, documents and photos are leading skeptics to dismiss as tall tales the stories of off-world UFOs stored by secret government programs.
Military intelligence officials who have voiced their support for Grusch since he came forward publicly point out that he has placed himself at considerable risk if he is lying – as all his claims have been submitted to the DoD and Intelligence Community Inspector Generals on penalty of perjury.