Doreen Lawrence today attacked the original police investigation into her son's murder, saying that detectives "failed miserably" to find his killers back in 1993.
She thanked jurors for finding Gary Dobson and David Norris guilty but said it was not a cause for celebration.
Speaking outside the Old Bailey, Mrs Lawrence said: "Had the police done their job properly, I would have spent the last 18 years grieving for my son rather than fighting to get his killers to court."
Mrs Lawrence said her relief at the verdicts was mixed with anger that she and her family were put through nearly two decades of "grief and uncertainty" not knowing if or when they would get justice.
"These verdicts will not bring my son back. How can I celebrate when I know that this day could have come 18 years ago if the police who were meant to find my son's killers (had not) failed so miserably to do so?" she said.
Mrs Lawrence warned against using today's convictions as evidence that racial discrimination in Britain was now a thing of the past.
"The fact is that racism and racist attacks are still happening in this country, and the police should not use my son's name to say that we can move on," she said.
She said she wanted people to think of Stephen as something other than a murdered black teenager.
"I now want people to remember him as a bright, beautiful young man who any parents of whatever background would have been proud of," she said.
"He was a wonderful son and a shining example of what any parent would want in a child. I miss him with a passion. Hopefully now he can rest in peace."
Stephen's father Neville said he was conscious there were five or six attackers that night and that he didn't think he would "be able to rest until they are brought to justice".
"I have not been able to rest all this time," Mr Lawrence said in a statement read outside court by his solicitor, Jocelyn Cockburn.
"I am therefore full of joy and relief that today, finally, two of my son's killers have been convicted of his murder.
"They will be sent to prison and face the consequence of their actions."