Stephen Lawrence's mother Doreen said she had to "hold" herself from screaming when she heard the jury pronounce two men guilty of her son's murder.
The campaigner described how she still speaks to her son when she visits the spot where he died on a pavement in Eltham, south-east London, in 1993.
Speaking on Desert Island Discs, she said: "During the trial I couldn't read the jury, I couldn't tell and so my heart was in my mouth when we went back downstairs and when they said guilty I suppose I had to hold myself in from screaming out because I had the press on one side, because I never thought I'd hear those words, I never thought I'd hear someone found guilty of Stephen's death."
Mrs Lawrence, who was made an OBE in 2003 and runs a trust set up in her son's name, chose a song called You're Loved which was inspired by some of the last words spoken to her son by a couple who found him dying in the street.
She said: "For me it meant so much that the couple.. said to him 'you're loved'."
Mrs Lawrence said she visits times a year the spot where he died three.
She said: "I go on the anniversary of his death, I go on his birthday and I go at Christmas time and I bring flowers for him and I stay as long as I can because I always feel a bit nervous when I'm there and I talk to him, tell him the news."
Earlier this month, it was announced that a leading barrister will review the Scotland Yard investigation into allegations of corruption at the heart of the case.
David Norris and Gary Dobson were convicted of the racist murder of the teenager in January this year - 19 years after the crime - and sentenced to life at the Old Bailey.
The Metropolitan Police faced fierce criticism of the original investigation and a public inquiry branded the force institutionally racist.