The teenager whose film of George Floyd’s death sparked global protests said she “stays up apologising” to him for “not doing more”.
Darnella, now 18, was one of four young witnesses to take the stand on the second day of Derek Chauvin’s trial.
She told the court of seeing Mr Floyd “begging for his life”, comparing him to her dad, brother, cousins and uncles “because they are all black”.
Issues of racial equality and policing lay at the centre of the case.
On Monday, the opening session of the trial heard Mr Chauvin, an ex-police officer, knelt on Mr Floyd’s neck for over nine minutes while arresting him in Minneapolis in May 2020. Prosecutors say this was a “major cause” in his death.
Defence lawyers have indicated they will argue that 46-year-old Mr Floyd died of an overdose. Mr Chauvin, 45, denies charges of murder and manslaughter.
Three other officers who were present – Tou Thao, J Alexander Keung and Thomas Lane – will go on trial later in the year.