On its Web site, the TSA says it has built "strict privacy safeguards" into its use of the advanced imaging technology. Officers who view the images never see the passengers being scanned and the images blur facial features. In addition, the units cannot store, print, transmit or save the images.
But German said "everything is in implementation."
"Human nature is you're curious and you're doing things you shouldn't do if there isn't strict oversight and accountability," he said. The powerful scanners can expose embarrassing medical equipment and prosthetics, he said, adding that electronic images can spread very quickly.
However, he added, if the manufacturers and the TSA can prove that the technology is effective, then he said it's important to discuss the methodologies that could best protect privacy.
Joe Reiss, vice president of marketing for American Science & Engineering, a Billerica, Mass. manufacturer of backscatter units, said "The backscatter X-ray gives the best detection capability of the widest array of threats."
His units are not used by the TSA but are used in prisons, border checkpoints and other military installations.
As for the privacy issue, he said that in pilot programs, 85 percent to 90 percent of passengers elect the scanner over the pat-down. On its Web site, the TSA says that more than 98 percent of passengers who encounter scanning technology during pilot programs prefer it over other screening options.
"To me, that's the answer to the privacy concern. They want to be protected. They don't want to worry about threats like Northwest Flight 253," Reiss said.
But others argue that when it comes to homeland security issues, funds are better spent elsewhere.
"Airport security is the last line of defense and not a very good one," said Bruce Schneier, a security technologist and author. "You pick a defense, [terrorists] look at it and then they pick an attack you haven't thought of."
He argued that it's "magical thinking" to attempt to thwart terrorist attacks by reacting to their last threats. Instead, he said, the government should boost investigation and intelligence efforts.
Isaac Yeffet, former head of security for the Israeli airline El Al, argued that people, not technology, hold the keys to enhanced public safety.
"The best security is not technology, the best security is a qualified and well-trained human being," he said.
Instead of deploying the revealing -- and potentially embarrassing -- full-body scans, Yeffet advocated for higher investments in airport security personnel.
He said security staff should be college grads, fluent in at least two languages and trained to authenticate travel documents and carefully question passengers about their travels.
"I want to make sure that when you talk to the passenger, you talk to every passenger and look them in the eyes," he said. "I have to ask all the questions. ... Through your answers, here I can determine if you are bona fide or suspicious."
Trained airport personnel can detect irregular body language and dubious explanations, but technology can't he said, adding, "I use technology to help me, not replace me."