in the staircase vs in the staircases

Some examples from the web:

• He's standing there in the staircase.
• A slug was recovered from the rink wall there, another one up in the staircase there.
• To preserve his dreams of one day owning an artallery in mexico, jackson decided to bury his Stolen treasure in the staircase of the seemingly abandoned property.
• In the staircase from the First Floor of access to coverage to the terrace, we have made the steps and related glass railings laminated safety glass type Extrawhite.
• Explosion in the staircase.
• They'll get their tan in the staircase
• You were eight and you got your head stuck in the staircase banister.
• The vacation rental is well located (an 8 minute walk from the subway) and the building is quiet and clean (even though there were works going on in the staircase).

Some examples from the web:

• You were eight and you got your head stuck in the staircase banister.
• He's standing there in the staircase.
• A slug was recovered from the rink wall there, another one up in the staircase there.
• In the staircase from the First Floor of access to coverage to the terrace, we have made the steps and related glass railings laminated safety glass type Extrawhite.
• The vacation rental is well located (an 8 minute walk from the subway) and the building is quiet and clean (even though there were works going on in the staircase).
• To preserve his dreams of one day owning an artallery in mexico, jackson decided to bury his Stolen treasure in the staircase of the seemingly abandoned property.
• They'll get their tan in the staircase
• It's poplar, most likely from the staircase in the house.