Mr Pieknyi, a Romanian national who came to the UK two months earlier and lived in Milton Keynes, was found suffering from stab injuries.
Vladyslav Yakymchuck, 22, a Ukrainian national, has been charged with murder, three counts of robbery, one count of theft and possession of a bladed article.
Oluwatimilehin Oniyitan, 20, from Eltham, Ibrahim James, 21, from Plumstead, Dominic Brown, 29, from Woolwich, Andrew Adekoya, 21, and Abaraye Campbell, 21, have been charged with murder.
He had been awarded the National Police Bravery Award in July 2009 after he intervened to stop a rape.
The killers used a black BMW estate which was stolen from Stratford.