El robo de la monalisa

The Discovery
Everyone had been talking about the glass panes that museum officials at the Louvre had put in front of several of their most important paintings. Museum officials stated it was to help protect the paintings, especially because of recent acts of vandalism. The public and the press thought the glass was too reflective.
Louis Béroud, a painter, decided to join in the debate bypainting a young French girl fixing her hair in the reflection from the pane of glass in front of the Mona Lisa.
On Tuesday, August 22, 1911, Béroud walked into the Louvre and went to the Salon Carré where the Mona Lisa had been on display for five years. But on the wall where the Mona Lisa used to hang, in between Correggio's Mystical Marriage and Titian's Allegory of Alfonso d'Avalos, sat onlyfour iron pegs.
Béroud contacted the section head of the guards, who thought the painting must be at the photographers'. A few hours later, Béroud checked back with the section head. It was then discovered the Mona Lisa was not with the photographers. The section chief and other guards did a quick search of the museum -- no Mona Lisa.
Since Théophile Homolle, the museum director, was on vacation,the curator of Egyptian antiquities was contacted. He, in turn, called the Paris police. About 60 investigators were sent over to the Louvre shortly after noon. They closed the museum and slowly let out the visitors. They then continued the search.
It was finally determined that it was true -- the Mona Lisa had been stolen.
The Louvre was closed for an entire week to aid the investigation.When it was reopened, a line of people had come to solemnly stare at the empty space on the wall, where the Mona Lisa had once hung. An anonymous visitor left a bouquet of flowers.1
"[Y]ou might as well pretend that one could steal the towers of the cathedral of Notre Dame," stated Théophile Homolle, museum director of the Louvre, approximately a year before the theft.2 (He was forced to resign soonafter the robbery.)
The Clues
Unfortunately, there wasn't much evidence to go on. The most important discovery was found on the first day of the investigation. About an hour after the 60 investigators began searching the Louvre, they found the controversial plate of glass and Mona Lisa's frame lying in a staircase. The frame, an ancient one donated by Countess de Béarn two years prior, had notbeen damaged. Investigators and others speculated that the thief grabbed the painting off the wall, entered the stairwell, removed the painting from its frame, then somehow left the museum unnoticed. But when did all this take place?
Investigators began to interview guards and workers to determine when the Mona Lisa went missing. One worker remembered having seen the painting around 7 o'clockon Monday morning (a day before it was discovered missing), but noticed it gone when he walked by the Salon Carré an hour later. He had assumed a museum official had moved it.
Further research discovered that the usual guard in the Salon Carré was home (one of his children had the measles) and his replacement admitted leaving his post for a few minutes around 8 o'clock to smoke a cigarette. All ofthis evidence pointed to the theft occurring somewhere between 7:00 and 8:30 on Monday morning.
But on Mondays, the Louvre was closed for cleaning. So, was this an inside job? Approximately 800 people had access to the Salon Carré on Monday morning. Wandering throughout the museum were museum officials, guards, workmen, cleaners and photographers. Interviews with these people brought out verylittle. One person thought they had seen a stranger hanging out, but he was unable to match the stranger's face with photos at the police station.
The investigators brought in Alphonse Bertillon, a famous fingerprint expert. He found a thumbprint on the Mona Lisa's frame, but he was unable to match it with any in his files.
There was a scaffold against one side of the museum that was there to...