three of the convicted bomber 's family members said they believe dzhokhar tsarnaev was the victim of a conspiracy .
an uncle said ` american special services ' orchestrated the 2013 terrorist attack which left three dead and hundreds more wounded .
tsarnaev was found guilty by a boston jury on april 8 of all 30 counts - 17 of them carrying the death penalty .
the death penalty phase of his trial begins on april 21 .