The answer to this question is no.  The conscience is not a reliable guide because it is not the same in all people.  You might say that conscience is a reflection of the rights and wrongs that one has been taught through life, and so what conscience dictates for some may be different from what conscience dictates for another.  God’s laws are not so subjective that they can be vary based upon who is doing what, rather they are concrete laws of right and wrong (note that this is not a discussion of matters of opinion where conscience does play a role).  Conscience is something that can be conditioned, as I Timothy 4:2b reads, “having their conscience seared with a hot iron.”
    Some people simply cannot use conscience as a reliable guide.  A serial killer in the early part of this century was sent to Leavenworth.  This character was as hardened a criminal as you would hope to find.  After some time in the “big top” he was quoted as saying, “I wish all the world had one big neck . . . so I could choke it.”  Pardon me if I missed something, but it sounds like his conscience would not hinder him from killing again.  We would all agree in that extreme case conscience would not be a reliable guide.
    To take an example from the Bible we look to another killer.  We look to one who was killing Christians in the first century (Acts 22:4).  Paul had killed God’s own people, and he had done it with a clean conscience (Acts 23:1).  Did not violating his conscience make it right?
    Conscience is not a reliable guide in determining what is right.  We should all try to train our consciences, and parents train our children’ consciences, so that when we do something we are cognizant of it.  But at the same time we should never be so naïve as to think that if we don’t feel wrong about doing something then it must not be wrong.