One of my police detectives has asked me to find an offense to charge a mother that has asked 2 witnesses to lie to the police about her son's involvement in a crime. The witnesses did not lie, so no party to a False Report to Peace Officer. She did not offer any benefit for lying, so there goes Tampering with a Witness (also no official proceeding, yet). There is no physical evidence involved, so no party to Tampering with Evidence. She did not threaten any harm to them if they told the truth, so no Obstruction or Retalation.

Surely it is illegal to ask witnesses to lie for you or am I just naive!

I have not seen an attempt to commit perjury prosecuted, but it seems to me the mom did an act amounting to more than mere preparation that tended but failed to effect the commission (by a party for whose conduct she would have been responsible under 7.02(a)) of the offense intended. But, maybe the fact that 15.03 is limited to more serious offenses means its ok to ask another to consider perjury so long as you offer no inducement.

My gut feeling is that unless the Legislature specifically makes it an offense to "offer" or "solicit" a specific crime, you're generally out of luck. There's a dozen or so "offer"-type crimes, but this isn't one of them (as far as I can tell).