tsarnaev , 21 , was found guilty wednesday on all 30 charges related to the 2013 boston marathon bombing .
his case will now proceed to the penalty stage , in which the jury will decide whether to sentence him to life in prison or execution .
reflecting her state 's liberal politics , warren is against capital punishment .
warren also spoke about current party issues - but refused to compare her politics to those of likely presidential candidate hillary clinton .
warren has repeatedly said she will not be running for president in 2016 .