The image of Lady Justice is a common symbol on courthouse walls. It symbolizes fair and equal conduct of the law, without corruption, favor, greed or prejudice. Lady Justice originates from Ancient Roman art as Iustitia or Justitia after who is equivalent to the Greek goddesses Themis and Dike.

Many embedded symbols can be found in the image of Lady Justice: 

The blindfold represents objectivity and impartiality, that justice should be carried out regardless of fear, favor, wealth or power. 

The scales represent the weighing of the evidence by its own merit. 

The sword represents the swiftness, unambiguity and finality of the verdict. 

The snake between her feet represents the world of evil and lies

The book underneath is the constitution from which justice is derived. 

for more information see https://civicsonlineresourcecommunity.org/meaning-of-lady-justice