Many people here are miffed that you haven't use the search feature to look for this answer, but to directly answer you:
You can NOT jailbreak 6.1.3 nor 6.1.4 untethered on any device right now.
Will it ever be possible? Well looks like there will be one when iOS 7 is released. The hacking groups have hinted that they are saving exploits up to crack iOS7.
You should bookmark this site: http://www.iclarified.com/jailbreak/ as it will immediately tell you when a jailbreak is out for your device. If you want to punish yourself, then subscribe to evador's twitter, but I find that maddening to try to decipher the stream of consciousness of those folks.