[Netizen]

Luke 1
5   THERE was in the days of Herod, the king of Judaea, a certain priest named Zacharias, of the course of Abia: and his wife was of the daughters of Aaron, and her name was Elisabeth.
6   And they were both righteous before God, walking in all the commandments and ordinances of the Lord blameless.

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Blameless is different from sinless.

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Let's look at them both, closer.

1) blameless, deserving no censure, free from fault or defect

sin(less)
1) to be without a share in
2) to miss the mark
3) to err, be mistaken
4) to miss or wander from the path of uprightness and honour, to do or go wrong
5) to wander from the law of God, violate God's law, sin

They didn't wander from God's commandments and ordinances.

[Truth-Miner]

I went to this site to see what the original Greek met in the use of the word blameless.

http://net.bible.org/verse.php?book=Luk&chapter=1&verse=6

At the bottom of the page I found this note:
tn Grk “walking in” (an idiom for one’s lifestyle).
sn The description of Zechariah and Elizabeth as following… blamelessly was not to say that they were sinless, but that they were faithful and pious. Thus a practical righteousness is meant here (Gen 6:8; Deut 28:9)

So sinless and blameless are not the same thing in this case. Just my opinion...