Mercy Muthoni and Joseph Muiruri appealed the sentence through lawyer Wahome Gikonyo.
Lawyer Gikonyo poked holes in the prosecution evidence saying there were discrepancies.
Lady Justice Rachel Ng'etich pointed out that the witnesses failed to connect the suspects with the stolen vehicle.
A man and woman who had been sentenced to death for robbery with violence have been set free by the High Court in Nyeri following an appeal.
Mercy Muthoni and Joseph Muiruri appealed the sentence through lawyer Wahome Gikonyo arguing that the trial court failed to call crucial witnesses in the case.
They were jointly charged that on September 12, 2013 at Lachuta Farm area in Kieni West they robbed Joseph Weru Murakaru one mobile phone, Sh18,000 cash and one motor vehicle make Toyota Succeed all valued at Sh722,500.
The court heard that they used force and violence to commit the offence.
Lawyer Gikonyo poked holes in the prosecution evidence saying there were discrepancies in description of the vehicle robbed from the complainant.
He said the registration number indicated in the charge sheet was KBM 522Y while the complainant in his testimony said his vehicle was KBA 592Y Probox.
The lawyer added that another witness gave registration numbers as KBN 522Y and that when the complainant was recalled he gave registration number of his vehicle as KBL 522L.
He submitted that there was glaring contradictions that gave rise to a question as to how many vehicles were involved in this robbery.
The lawyer faulted Senior Resident Magistrate Christine Wekesa for convicting the two suspects without any amendments done.
He added that police did not conduct identification parade and the complainant identified the suspects while they were in the dock during hearing.