The fan who caused a large pile-up during the first stage of this year's Tour de France has appeared in court. 

The 31-year-old woman has gone on trial in the western French city of Brest.

During the first stage of the race in Brittany, she stepped into the road to hold up a sign to the TV cameras. As she did, her sign clipped a rider who was knocked off, sparking a succession of riders to crash.

The woman's identity has been withheld after she was targeted by online abuse following the accident. 

After the crash, she fled the scene and remained in hiding for four days before turning herself in to police. She has already told prosecutors of being ashamed at her "stupidity."
 

What happened? 
 

The peloton was 45km from the end of the first stage of the 2021 edition. The pack was tightly bunched on a narrow road in the region of Brittany in northwest France. 

In footage from the day, the fan can been seen trying to get her hand-written sign seen by the TV crews who travel ahead of the cyclists. She is holding a placard with "granny and grandad" written in German. 

But the woman is looking away from the peloton and does not see them approach. 

Trying to ensure that her message is seen, she steps on to the edge of the road and unwittingly leans the sign into the path of the oncoming riders hitting German cyclist Tony Martin who was knocked off. 

Dozens of riders then crashed into each other and several of the competitors had to pull out of the race on the opening day due to the injuries that they sustained in the pile-up. 

Spain's Marc Soler broke both his arms. 

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The Switzerland-based International Association of Riders (CPA) is seeking a symbolic one euro in damages to send a message against dangerous fan behavior.

"An athlete prepares for months for a grand tour and it is not acceptable that all his hard work… should be shattered in an instant by the quest for popularity," CPA president Gianni Bugno said in a statement on the eve of the trial.

The woman is charged with endangering lives and causing unintentional injuries and she risks a fine of $17,300 and a year in prison if found guilty.

A lawyer for the cyclists said that they were seeking a four-month suspended sentence. The court has reserved its decision until December 9.