As things stand now in New York and most other jurisdictions there are no adequate means open to the State to find out the actual present or past mental condition of the defendant until the trial itself, and ofttimes not even then.
In New York, in cases like Thaw's, the accused, while fully intending to interpose the defence of insanity (which he is now permitted to do simply under the general plea of "not guilty") may not only conceal the fact until the trial, but may likewise successfully block every effort of the authorities to examine him and find out his present mental condition.

He may thus keep it out of the power of the District Attorney to secure the facts upon which to move for a commission to determine whether or not he ought to be in an insane asylum or is a fit subject for trial, and at the same time prevent the prosecutor from obtaining any evidence through direct medical observation by which to meet the claim, which may be "sprung" suddenly upon him later at the trial, that the defendant was irresponsible.
In order that this may be clearly understood by the reader he should fully appreciate the distinction between (1) the claim on the part of an accused that he is at present insane, and for that reason should not be either tried or punished for his alleged offence, and (2) the defence that he was (irrespective of his present mental condition) insane within the legal definition of irresponsibility at the time he committed it.

No person who is incapable of understanding the nature of the proceedings against him or of consulting with counsel and preparing his defence can be placed on trial at all, or, if already on trial, can continue to be tried, and if a defendant "appears to the court to be insane," the judge may appoint a commission to examine him and report as to his present condition.

This may be done upon the application either of the State of the accused through his counsel.
It was such a commission to determine the accused's present mental condition that District Attorney Jerome, upon the basis of the evidence introduced by the defence, applied for and secured during the first trial of Harry K.Thaw.The commission reported that Thaw was sane enough to be tried and the court then proceeded with the original case for the purpose of allowing the jury to say whether he knew the nature and quality of his act and that it was wrong when he shot and killed White.
This was a totally distinct proceeding from the interposition of the DEFENCE that the accused was irresponsible when he committed the crime charged against him and was not inconsistent with it.
Now supposing that the Commission had reported that Thaw was insane at the time of examination and not a fit subject for trial, but, on the contrary, ought to be confined in an insane asylum, the District Attorney would have spent some twenty odd thousand dollars and a year's time of one or more of his assistants in fruitless preparation.

Yet, as the law stands on the books to-day in New York, there is no adequate way for the prosecution to find out whether this enormous expenditure of time or money is necessary or not, for it cannot compel the defendant to submit either to a physical or mental examination.