Campaigners are calling on the government to change a law which allows several people to be prosecuted for crimes such as murder - even though they may have played different roles in the offence.
Families from all over the country will hand in a petition of more than 10,000 signatures to Downing Street protesting against the 'Joint Enterprise' law.
They say it's unfair and affects black and ethnic minorities more than any other group.
Two of the campaigners, Charlotte Henry and Deb Madden, explain more.