Ariel O'Connor, an objects conservator for the Smithsonian American Art Museum, looks into the "Three Room Dwelling" Nutshell crime diorama. (Barbara Haddock Taylor/Baltimore Sun)

Using a tiny paintbrush, Ariel O’Connor carefully applied a compound to preserve the charred wall of a dollhouse featuring a grisly scene: The skull of a body lying in a bed inside peers out, beseeching the viewer to determine whether this was murder.

The dollhouse is one in a series of model whodunits used to train generations of police detectives in crime scene investigation. It is being cleaned, repaired and stabilized to be showcased at the Smithsonian American Art Museum’s Renwick Gallery beginning in October. It is the first time the collection, built about 70 years ago, will be on public display.

“The location of everything in here is important and could be a clue,” said O’Connor, a Smithsonian conservator who is spending three months at the office of the chief medical examiner in Baltimore working on the tableaus.

The “attention to detail is unbelievable,” she said. “You can see the craftsmanship on such a miniature scale.”

The exhibition, “Murder Is Her Hobby: Frances Glessner Lee and the Nutshell Studies of Unexplained Death,” will be on display from Oct. 20 to Jan. 28, 2018. Visitors will be given flashlights and magnifying glasses to inspect the 19 dioramas, including “Pink Bathroom,” which depicts a widow found dead in her apartment by the building’s janitor. They will also be given access to the crime scene reports that investigators would receive during training. The solutions, however, will remain secret.

Lee was a wealthy Chicago heiress who helped establish a forensic pathology program at Harvard University, earning her the title “godmother of forensic science.” She meticulously built the dollhouses — with the help of a carpenter beginning in the 1940s to portray homicides, suicides, and accidental and inexplicable deaths.

They have been housed at the medical examiner’s office in Baltimore since 1966. Maryland’s medical examiner at the time, Russell S. Fisher, brought them here after Harvard’s Department of Legal Medicine closed. The models remain on indefinite loan from Harvard Medical School.

Not allowed to attend college, Lee got married at 19 and had three children, but later divorced. Years later, as her interest in forensics grew, she endowed a legal medicine department at Harvard in 1931, establishing herself in the new field.

Lee died in 1962 at age 83.

Nora Atkinson, the exhibit’s curator, said her work provides a window into the domestic lives of women and the working class. Lee focused on the “‘invisible” members of society, such as impoverished and female victims, and the details she included in her dioramas challenge the association of femininity with order and domestic bliss.

“She is calling into question all of the assumptions,” Atkinson said. “This is the first time any of these are being seen in an art context versus a science context. . . . It’s a ‘woman in a man’s world’ and a ‘search for truth.’ It’s a wonderful story on so many levels.”

The Smithsonian approached the medical examiner with the request to put the dioramas on exhibit after Atkinson found details about them while researching another artist.

Bruce Goldfarb, spokesman for the examiner’s office, said allowing them to go on public display came with the opportunity to have the Smithsonian undertake the expensive process of conserving Lee’s work. A less exhaustive conservation effort was undertaken in the early 1990s.

Goldfarb said the project is desperately needed. The dioramas have been deteriorating, bulbs have burned out, pieces have come loose and fabrics are wearing. Some crimes can’t be interpreted as Lee intended them because of aging. For example: Fake blood on the widow’s face in “Pink Bathroom” has turned purple, wrongly suggesting decomposition or asphyxiation.

“They are at a point now that things were cracking and crumbling and had they not been attended to very quickly, things would have broken to the point that would have been irreparable,” he said. “They came at just the right time.”

A Smithsonian spokeswoman said the museum did not have a tally for the cost of the conservation work, which is taking about three months. The museum also did not provide the amount of the exhibition’s overall budget.

When the exhibit is over, the nutshells will return to Baltimore to be used for the annual Frances Glessner Lee Seminar in Homicide Investigation next spring, Goldfarb said.

The dioramas offer valuable training lessons even with today’s technology, he said.

“There is no other way to learn to see; it’s about training to observe,” Goldfarb said. “These three-dimensional representations do something that can’t be done by any other medium. . . . They are like a real crime scene — as detailed and overwhelming.”

Lee, who built the miniature models at her New Hampshire estate, based the scenes on real crimes in New England using witness statements, police reports and her own embellishments. The goal was to train homicide investigators to “convict the guilty, clear the innocent and find the truth in a nutshell.”

There were 20 nutshells originally, some single rooms, some entire houses. The bulk, 18, have been at the medical examiner’s office. One was ruined years ago in transit. The last one was discovered in the attic of Lee’s estate and has been on long-term loan to the Bethlehem Heritage Society in New Hampshire.

Lee spent $6,000 to $8,000 to build each one, roughly the cost to construct an actual house at the time. She used real tobacco to roll miniature cigarettes, knitted tiny stockings for her porcelain dolls and hand-painted a design on the floor of a bedroom scene to hide a clue.

In “Barn,” a porcelain doll is displayed with its feet crashed through a wooden crate and hanging from a rope — the barn hoist — with a noose around its neck. The elaborate scene shows the figure, a man, dressed in a blue shirt, trousers and suspenders. There’s a wooden saw horse and hay stuffed into a loft behind him. The scene is viewed through a pair of open wooden barn doors.

The diorama depicts a fictitious farmer, “Eben Wallace,” found dead on July 15, 1939. His wife, “Imelda Wallace,” told police in an eight-sentence statement that her husband was hard to get along with and would sometimes go to the barn to threaten suicide. He would stand on a bucket with a noose around his neck until she would persuade him to get down. On the day of his death, she had been using the bucket at the pump. Her husband had stood instead on the wooden crate.

Was it murder or suicide?

During a recent visit to the medical examiner’s office, O’Connor, the Smithsonian conservator, had removed the back of the barn for reconditioning. To figure out what materials the doll is made from and whether it has lead shot in its legs to give it weight, she plans to run the tiny body through an

X-ray.

Loose pieces from a wood pile were lined up next to a miniature ax — complete with a rusted blade — and a water pump, all for O’Connor and partner Haddon Dine to work on.

Visible on the back of the barn is a hand-colored photograph of New Hampshire’s White Mountains that Lee placed behind a faux window to create a scenic backdrop.

A major part of the conservation project is new light installation. A Smithsonian lighting expert produced circuit boards to develop tiny, low-heat LED electronics and glass bulbs. The old bulbs give off heat, accelerating the destabilization of the models.

The barn and the other dioramas will be transported to the Washington museum on a special truck, stowed inside custom-made transport boxes to minimize the effects of the truck’s vibration, O’Connor said. They will be placed in plexiglass display cases so they can be inspected from all sides.

To restore the pieces as Lee intended them, O’Connor depends on her carefully trained eye. She looks for clues, just like a crime scene investigator: glue residue that reveals the original placement of a can of spaghetti or an ultraviolet light that exposes faded pencil markings.

“I didn’t know the parallels between the field of forensics science and the field of art conservation,” O’Connor said. “The way we approach conservation treatments is quite similar to how detectives would approach crime scenes. We start with documentation and understanding exactly how things are.

“Before we touch anything, we want to know where everything is.”

An earlier version of this story stated that the dollhouses had been housed at the medical examiner’s office in Baltimore after Harvard sought to discard them. The dollhouses were brought to Baltimore after Harvard’s Department of Legal Medicine closed. They remain on loan from Harvard Medical School.