Did the St. Louis County prosecutor admit to a violation of the rule regarding perjury?

Below you will find a video of a radio interview with Bob McCulloch, the St. Louis County prosecutor who handled the Grand Jury proceeding against Darren Wilson in Ferguson, Missouri.  The interview is interesting for many reasons, but the part that really caught my attention was the discussion about the possibility that some of the witnesses committed perjury.

This discussion starts at the 9 minute mark of the recording.  The interviewer asks "Why did you allow people to testify in front of the grand jury in which you knew their information was either flat-out wrong, or flat-out lying, or just weren't telling the truth?" In response, McColluch is vague as to whether he agrees with the premise of the question (that he knew some of the witnesses were not telling the truth), but later he specifically says it was clear some of the witnesses were not telling the truth and, further, admits that he would not normally use witnesses like those - that he did that specifically for this one case. Later he adds that he was "absolutely sure" that some witnesses lied under oath, but that he would not seek perjury charges (at minute 16:15 or so).

Was that an admission that he knowingly presented false evidence/perjured testimony?

Are the rules related to grand juries so different that they allow the knowing use of false evidence in an effort to have the jury assess credibility?  That is how McCulloch tries to explain his conduct. He states that "I knew that no matter how I handled it, there would be criticism of it. So if I didn't put those witnesses on, then we'd be discussing now why I didn't put those witnesses on. Even though their statements were not accurate. So my determination was to put everybody on and let the grand jurors assess their credibility, which they did. ...I wanted to put everything on there. I thought it was much more important to present everything and everybody, and some that, yes, clearly were not telling the truth. No question about it."

If the prosecutor was so concerned with how "we'd be discussing now why I didn't put those witnesses on," let try this on for size: How about stating "because I have an ethical obligation not to put those witnesses on the stand.  Those witness are lying and the system can't function if we allow prosecutors to knowingly use false evidence."  That wouldn't be so difficult, would it?

I understand the prosecutor's decision to allow the witnesses to testify if he merely believed, but did not know, that they were lying. That essentially means he thought they had poor credibility and that it would be better to let the jury assess that credibility.  Allowing witnesses to testify when you have doubts as to whether they are telling the truth (as long as there is no knowledge) is not a violation of the rules.  But the prosecutor here used different language. He essentially said he knew they were lying. Once you have knowledge, the rule is clear.

Maybe the prosecutor meant the former but said the latter.  Otherwise, I think he admitted to using false evidence. I should clarify that this is not an admission of suborning perjury because suborning suggests he encouraged the witness to lie. Here what he seems to admit to is allowing someone to testify falsely when he knew they were lying. That is not suborning perjury but it is knowingly using false evidence which is a violation of Rule 3.3.

In the end, the question is whether the comments should be interpreted to mean he knowingly violated the rules or that he merely had doubts as to the credibility of the witnesses and allowed the jury to decide, which would not be a violation of the rules.  

Here is the video: