Luke 23

Luke23:39 Then one of the criminals who were hanged blasphemed Him, saying, “If You are the Christ, save Yourself and us.” (NKJV)

Here in the English transaltion it says that one of the criminals who were hanged "blasphemed" Jesus. In the NIV translation it says something similar: "One of the criminals hurled insults at him".
I have been thinking about why he does this, although he is already at the end of his life. Normally people who are just before their death have already finished with their life in their heart. And so I think there were two reasons for his "hurling of insults" at Jesus:

1) Since he has already finished with his life in his heart he didn't care about anything anymore. He could do whatever he wanted to do because he wouldn't have to care about the mess he made afterwards. And so he took this opportunity to "hurl" and throw the insults at Jesus in order to feel a bit better and just to have at least a bit of fun in the last few hours of his life. He just did the same as the rulers and the soilders did (... talking about this I would think of something similar like "peer pressure"). He joined them in their mocking.

2) He might still have had a bit of hope in being saved. Comparison of the words the rulers said and the criminal said:
"If you are the king of the Jews, save yourself." (V.37) - rulers
"Save yourself and us!" (V.39) - criminal
He "challenged" Jesus in his power and in his might. If Jesus would have done what he said - in order to "win" this challenge - then Jesus would not have only demonstrated his great power to the criminal, but the criminal could also escape from death.

What this criminal does is a very logical reaction to his situation (since he was a criminal his thoughts wouldn't be very nice). But his focus was not on the things that would be AFTER his death but he focused on how to escape death and how to "enjoy" (well... at least having a bit of fun) the last few moments of his life.