What turns people into liars, cheaters and thieves?

The Government Accountability Office recently gave a detailed accounting of how employees in some of the biggest federal agencies filched commuter passes and then sold them online.

But it didn’t explain why they would engage in petty fraud that adds up to at least $17 million, probably more.

Why would you apply for public transport passes knowing that you actually ride to work with someone else? Why would you state in writing that you’re eligible for the benefits and won’t transfer or sell them, and then list them for bid on eBay?

Why would you – as one brazen huckster did – seal a deal over your government e-mail and then wear your Air Force uniform to meet the would-be buyer?

What were these “public servants” thinking while they picked our collective pocket?

A Federal Highway Administration lawyer who collected fare cards while on maternity leave and then sold them on eBay claimed that she didn’t know it was illegal – even though the warnings were right there on the paperwork she signed and on the backs of the passes themselves.

Did the Internal Revenue Service employee who parked for free but sold transit passes online try an ignorance-of-the-law excuse upon being accused of also stealing government computers and components that made it to eBay?

In the grand scheme of a $2.4 trillion federal budget and an $8.8 trillion national debt, government workers stealing essentially hundreds or thousands of dollars might seem trivial. Except that the public transit subsidy program costs taxpayers more than $250 million annually for 233,000 workers, 106,000 of them in the Washington region. And the GAO’s investigation covered only a fraction of the agencies that provide the benefits.

But beyond that, the sneaks traced by the GAO worked at agencies such as Transportation, State, Defense and Homeland Security, the IRS and the Coast Guard. Knowing that you can’t trust some of the worker bees who keep the government humming doesn’t exactly build confidence.

Some of the documented examples are so pedestrian that they’re almost funny.

The Air Force captain wouldn’t come down on his price ($350 for $420 worth of fare cards) for fear of his wife’s wrath.

A State Department seller who advertised on Craigslist wanted cash ($160 for $210 worth of fare cards) to buy Christmas gifts.

A Treasury secretary who collected twice what her commute cost used extra fare cards for her son’s school transportation and sold some to friends and Treasury contractors.

I asked Katherine Farquhar, an American University professor with expertise in organizations and public affairs, why people might do things so obviously wrong but not entirely surprising.

She suggested possibilities: Maybe they’re frustrated with their agency, they feel short-changed, they’re resentful, they feel unrecognized or they consider the passes an entitlement.

I wondered whether midlevel employees get cynical when they hear about a presidential adviser pleading guilty to fleecing Target out of refunds or an Education Department official owning stock in a company that his agency oversees.

Without diminishing individuals’ personal responsibility, you can’t ignore the blame of agencies that don’t enforce the same kinds of rules that apply to other government benefit programs: checking addresses, making sure that applicants give accurate information, and requiring recipients to regularly recertify their eligibility.

The Treasury Department, of all places, was paying transit benefits to at least 25 people who’ve never worked there, the GAO reported.

Several officials assured members of Congress that they were tightening procedures and oversight. So maybe the managers will keep a closer eye on potentially sneaky fingers.

But I keep thinking about my father, who during 28 years as a federal employee wouldn’t even read the newspaper or a magazine at work unless it was on his lunch break so he wouldn’t deprive his employer of a full day’s work.

And I lament that we have to pay government workers to ensure that government workers stay honest.