The bible makes it very clear that there can be NO forgiveness for taking a life. The Psalms are only a series of poems, NOT the word of God as handed down.
It is not clear
It is much debated whether murder is the so called unforgivable sin or not ...
Here is one translation of line 14 of Psalm 51
"Rescue me from the guilt of murder, O God, the God who delivers me! Then my tongue will shout for joy because of your deliverance."
You can find this particular translation here :
http://biblehub.com/net/psalms/51.htmIt is a modern translation which is why it uses the word murder and not the old fashioned blood guilt
It is clear that Psalm 51 is a call for forgiveness after murder ...
Whether or not God does actually forgive murderers is a whole different debate ...
The meaning of line 14 of Psalm 51 is however beyond debate - it is crystal clear ...