Here are some California cases that discuss the issue, but I&#x27;m pretty sure federal law and the law of most states is similar:<p>The prosecution has no “duty to conduct the defendant’s investigation for him.” People v. Verdugo, 50 Cal. 4th 263, 288–89 (2010) (citation and internal quotations omitted); People v. Williams, 58 Cal. 4th 197, 257 (2013); People v. Zambrano, 41 Cal. 4th 1082, 1134 (2007), overruled on other grounds, People v. Doolin, 45 Cal. 4th 390, 421 n.22 (2009); People v. Salazar, 35 Cal. 4th 1031, 1048–50 (2005).<p>Because “the law does not ‘impose a general duty on prosecutorial officials to serve as defense investigators,’ ” People v. Moore, 50 Cal. App. 3d 989, 993 (1975) (quoting People v. Beagle, 6 Cal. 3d 441, 450–51 (1972), superseded on other grounds, Cal. Const., art. I, § 28), police are not generally required to collect particular items of evidence, People v. Montes, 58 Cal. 4th 809, 837 (2014); In re Michael L., 39 Cal. 3d 81, 86 (1985) (“police cannot be expected to gather up everything which might eventually prove useful to the defense”) (citation and internal quotations omitted); People v. Frye, 18 Cal. 4th 894, 943 (1998) (“as a general matter, due process does not require the police to collect particular items of evidence”), overruled on other grounds, People v. Doolin, 45 Cal. 4th 390, 421 n.22 (2009); People v. Callen, 194 Cal. App. 3d 558, 561 (1987) (“[The] law does not impose upon law enforcement agencies the requirement that they take the initiative, or even any affirmative action, in procuring … evidence deemed necessary to the defense of an accused.”) (citation and internal quotations omitted); People v. Bradley, 159 Cal. App. 3d 399, 407 (1984) (same).<p>Throw the case names and citations into Google Scholar to find the full text of the cases - which provide reasoning (unpersuasive, in my view).