"Delay in prosecution that occurs before the accused is arrested or the complaint is filed may constitute a denial of the right to a fair trial and to due process of law under the state and federal Constitutions. A defendant seeking to dismiss a charge on this ground must demonstrate prejudice arising from the delay. The prosecution may offer justification for the delay, and the court considering a motion to dismiss balances the harm to the defendant against the justification for the delay. A claim based upon the federal Constitution also requires a showing that the delay was undertaken to gain a tactical advantage over the defendant." (People v. Catlin (2001) 26 Cal.4th 81, 107, 109 (Catlin); see also 5 Witkin & Epstein, Cal. Criminal Law (3d ed. 2000) Criminal Trial, 282, p. 432.) The exact standard for due process violations under the United States Constitution "is not entirely settled. It is clear, however, that the law under the California Constitution is at least as favorable for defendant in this regard as the law under the United States Constitution." (People v. Nelson (2008) 43 Cal.4th 1242, 1251 (Nelson).) "Under California law, negligent, as well as purposeful, delay in bringing charges may, when accompanied by a showing of prejudice, violate due process." (Id. at p. 1255.) No matter the length of the delay, prejudice must be established and is not presumed. (Nelson, supra, 43 Cal.4th at p. 1250.) Prejudice "'may be shown by loss of material witnesses due to lapse of time or loss of evidence because of fading memory attributable to the delay.'" (Catlin, supra, 26 Cal.4th at p. 107.) The need to balance prejudice against justification arises only if the defendant establishes actual prejudice. If the defendant was not prejudiced by the delay, the reviewing court need not determine whether the delay was justified. (Scherling v. Superior Court (1978) 22 Cal.3d 493, 506 (Scherling).) If the delay was caused by further investigation, the justification for the delay is strong. (Nelson, supra, 43 Cal.4th at p. 1256.) "'Prosecutors are under no duty to file charges as soon as probable cause exists but before they are satisfied they will be able to establish the suspect's guilt beyond a reasonable doubt.'" (Ibid., quoting People v. Dunn-Gonzalez (1996) 47 Cal.App.4th 899, 914-915.) Whether a defendant has met the initial burden of showing prejudice is a question of fact that is reviewed on appeal under the substantial evidence standard. (People v. Dunn-Gonzalez, supra, 47 Cal.App.4th at p. 912, citing People v. Mitchell (1972) 8 Cal.3d 164, 167.) "The state and federal constitutional standards regarding what justifies delay differ." (People v. Nelson, supra, 43 Cal.4th at p. 1251.) However, "the exact standard under the federal Constitution is not entirely settled." (Ibid.) It seems clear that, under the federal standard, "delay undertaken to gain a tactical advantage over the accused . . . would violate due process if the defendant demonstrates prejudice." (Id. at p. 1253.) Some cases also suggest that "delay incurred in reckless disregard of circumstances known to the prosecution suggesting that delay might prejudice the defense would also violate due process if the defendant demonstrates prejudice." (Ibid.) Case law is less clear on whether "delay might be unjustified in other circumstances as well." (Ibid.) "It is clear, however, that the law under the California Constitution is at least as favorable for defendant in this regard as the law under the United States Constitution. Accordingly, we can and will apply California law." (Id. at p. 1251.) "Under California law, negligent, as well as purposeful, delay in bringing charges may, when accompanied by a showing of prejudice, violate due process." (People v. Nelson, supra, 43 Cal.4th at p. 1255.) "Whether the delay was negligent or purposeful is relevant to the balancing process. Purposeful delay to gain an advantage is totally unjustified, and a relatively weak showing of prejudice would suffice to tip the scales towards finding a due process violation. If the delay was merely negligent, a greater showing of prejudice would be required to establish a due process violation." (Id. at p. 1256.)