Yes, you can file with TurboTax for an incarcerated friend if you have a Power of Attorney that authorizes you to take that action on his/her behalf.
From @Rick19744 ,
"If your return is signed by a representative for you, you must have a power of attorney attached that specifically authorizes the representative to sign your return. To do this, you can use Form 2848.
You would include a copy of the form 2848 if you are filing a paper version.
If efiling, you would attach the form 2848 to the form 8453.
Form 8453 has a specific box to check if you are attaching a POA indicating that the individual has authority to sign the tax return:
Form 2848, Power of Attorney and Declaration of Representative (or POA that states the agent is granted authority to sign the return)
I would also recommend when you send in the form 8453 with the POA that you send this certified mail return receipt requested. That way you know that it was received by the IRS; inexpensive insurance !!"
