He has provided consulting services on the townhouse in the Brentwood section of Los Angeles where Nicole Brown Simpson, O. J. Simpson’s former wife, was murdered in 1994; the home in Boulder, Colo., where JonBenet Ramsey, age 6, was found strangled in 1996; and the mansion near San Diego where 39 members of the Heaven’s Gate cult committed mass suicide in 1997. (The Brentwood townhouse was bought in 1996 after the price was dropped; the Boulder home was bought in 1998 by a group of investors and is back on the market; and the mansion was torn down and a new home built on the site.)

Even Lizzie Borden’s house in Massachusetts, now a bed-and-breakfast, warranted a visit. “Time does heal a lot of those things, at least financially,” Mr. Bell noted.

In Newtown, where memories are still fresh, ownership of the house would have passed earlier this year from Ms. Lanza, who was divorced in 2009, through her estate to a surviving son, Ryan. Living out of state for some time, he showed little interest in salvaging the property and relinquished his claim on the house in return for being released from any further responsibility for the mortgage.

That cleared the way for Hudson City Savings Bank, as the entity that extended the mortgage, to take possession.

Beyond the loss that the bank expected to take on the mortgage, assuming the house proved unsalable, it had expended considerable money trying to make the property less of an eyesore. It replaced the plywood that had been used to secure the house after the police entered with proper doors. It hired people to manicure the lawn and tidy up the flower beds.

And it wanted to do more for the town, even though it does not have a branch in Newtown. “This is not about the money,” said Bill LaCalamito, a senior vice president in the mortgage-servicing department.

To accomplish that, it hired Mr. Bell to research all options.

One recommendation he made that was swiftly acted upon was to dispose of all contents and furnishings, down to the play set out back, in a way that would ensure that no disturbing souvenirs would turn up later.