COLD CASE INVESTIGATIONS WITHIN FAIRFAX COUNTY: TURNING THE LIABILITY OF TIME INTO AN ASSET

No department or individual involved in the investigation of homicides is ever going to have a 100% closure rate. Therefore, many departments will be faced with a situation where another homicide happens before they are finished handling the previous one. How does one manage these open cases; how often are they reviewed; and who is responsible once the assigned detective is either transferred or leaves the unit or department? Someone has to be able to answer questions from the family, media and anyone else who might inquire about the case. Based on the number of unsolved homicide cases within Fairfax County, the concept of a “Cold Case Squad” was explored. During January 1995, the Fairfax County Police Department implemented a Cold Case Squad consisting of one supervisor, three veteran detectives, two auxiliary police officers and one cadet. The Cold Case detectives inherited approximately 75 unsolved homicides which occurred in Fairfax County, Virginia, from 1964 through December 31, 1994. More than half of the unsolved homicides (42) have occurred in the past nine years. The hypothesis for this thesis was: The formulation of a Cold Case Squad would measurably reduce the number of unresolved homicides within Fairfax County. The primary evaluation factor for the thesis was the Cold Case Squad’s “close-ability” rate. The thesis identified and evaluated nine solvability factors utilized by the Cold Case Squad Supervisor. The solvability factors are considered when prioritizing case investigation, assigning personnel to an investigation and suspending investigate efforts. One of the goals for utilizing solvability factors is to develop a clear profile of cases with the most potential for close-ability. The study population for this thesis is the 42 unsolved homicides which have occurred in Fairfax County, Virginia, between January 1, 1986, and December 31, 1994. Solvability factor work sheets were completed and computated for the study population. The hypothesis has been proven as there is a measurable reduction in the number of unsolved homicides. From the study population, two cases have been closed by arrest, one case closed by exceptional means and one case is pending approval from the Commonwealth Attorney’s Office to obtain arrest warrants. These four cases represent a 9.5% reduction of unsolved cases within the study population. A copy of this thesis was given to the Cold Case Squad Supervisor for review and application. It is hoped the research from this thesis will be applied to the Cold Case Squad so it will become more effective and continue to turn the liability of time into an asset

Experimental data on growth, mortality, elemental composition and stable isotope composition

Individual data on survival, growth, %C, %N, C:N, d13C and d15N in Neomysis integer fed Artemia in different amounts

Tables S1-S5. Multiple comparison tests for life history traits. from Shifts in rotifer life history in response to stable isotope enrichment: testing theories of isotope effects on organismal growth

In ecology, stable isotope labelling is commonly used for tracing material transfer in trophic interactions, nutrient budgets and biogeochemical processes. The main assumption in this approach is that the enrichment with a heavy isotope has no effect on the organism growth and metabolism. This assumption is, however, challenged by theoretical considerations and experimental studies on kinetic isotope effects <i>in vivo</i>. Here, I demonstrate profound changes in life histories of the rotifer <i>Brachionus plicatilis</i> fed ¹⁵N-enriched algae (0.4–5.0 at%); i.e. at the enrichment levels commonly used in ecological studies. These findings support theoretically predicted effects of heavy isotope enrichment on growth, metabolism and ageing in biological systems and underline the importance of accounting for such effects when using stable isotope labelling in experimental studies

Figure S1. Food intake of Brachionus plicatilis exposed to 15N-enriched algal food. from Shifts in rotifer life history in response to stable isotope enrichment: testing theories of isotope effects on organismal growth

In ecology, stable isotope labelling is commonly used for tracing material transfer in trophic interactions, nutrient budgets and biogeochemical processes. The main assumption in this approach is that the enrichment with a heavy isotope has no effect on the organism growth and metabolism. This assumption is, however, challenged by theoretical considerations and experimental studies on kinetic isotope effects <i>in vivo</i>. Here, I demonstrate profound changes in life histories of the rotifer <i>Brachionus plicatilis</i> fed ¹⁵N-enriched algae (0.4–5.0 at%); i.e. at the enrichment levels commonly used in ecological studies. These findings support theoretically predicted effects of heavy isotope enrichment on growth, metabolism and ageing in biological systems and underline the importance of accounting for such effects when using stable isotope labelling in experimental studies

Mesozooplankton Grazing on Picocyanobacteria in the Baltic Sea as Inferred from Molecular Diet Analysis

<div><p>Our current knowledge on the microbial component of zooplankton diet is limited, and it is generally assumed that bacteria-sized prey is not directly consumed by most mesozooplankton grazers in the marine food webs. We questioned this assumption and conducted field and laboratory studies to examine picocyanobacteria contribution to the diets of Baltic Sea zooplankton, including copepods. First, qPCR targeting ITS-1 rDNA sequence of the picocyanobacteria <i>Synechococcus</i> spp. was used to examine picocyanobacterial DNA occurrence in the guts of Baltic zooplankton (copepods, cladocerans and rotifers). All field-collected zooplankton were found to consume picocyanobacteria in substantial quantities. In terms of <i>Synechococcus</i> quantity, the individual gut content was highest in cladocerans, whereas biomass-specific gut content was highest in rotifers and copepod nauplii. Moreover, the gut content in copepods was positively related to the picocyanobacteria abundance and negatively to the total phytoplankton abundance in the water column at the time of sampling. This indicates that increased availability of picocyanobacteria resulted in the increased intake of this prey and that copepods may rely more on picoplankton when food in the preferred size range declines. Second, a feeding experiments with a laboratory reared copepod <i>Acartia tonsa</i> fed a mixture of the picocyanobacterium <i>Synechococcus bacillaris</i> and microalga <i>Rhodomonas salina</i> confirmed that copepods ingested <i>Synechococcus</i>, even when the alternative food was plentiful. Finally, palatability of the picocyanobacteria for <i>A. tonsa</i> was demonstrated using uptake of ¹³C by the copepods as a proxy for carbon uptake in feeding experiment with ¹³C-labeled <i>S. bacillaris</i>. These findings suggest that, if abundant, picoplankton may become an important component of mesozooplankton diet, which needs to be accounted for in food web models and productivity assessments.</p></div

Quantities of <i>Synechococcus bacillaris</i> (ITS-1 copies ×10³ ind⁻¹and cells ×10³ ind⁻¹) detected in the live and dead individuals of the copepod <i>Acartia tonsa</i> (adults and nauplii) exposed to the picocyanobacterium in the feeding experiments (Experiments I and II).

<p>Data are shown as mean ± SD, <i>n</i> = 3 in all cases.</p

<i>Synechococcus</i> abundance (ITS-1 copies ×10³ ind⁻¹) detected in different mesozooplankton species/groups.

<p>Field-collected samples were used for the analysis. <i>E. affinis</i> – <i>Eurytemora affinis</i>, <i>Acartia</i> spp. – <i>Acartia bifilosa</i> and <i>A. longiremis</i>, <i>B. maritima</i> – <i>Bosmina maritima</i>, podonids – <i>P. intermedius</i> and <i>P. leuckartii</i>, rotifers – <i>Synchaeta</i> spp., <i>Keratella cochlearis</i> and K. <i>quadrata</i>; nauplii – <i>Acartia</i> spp. and <i>E. affinis</i>; <i>n</i> – number of samples analyzed.</p

Occurrence of <i>Synechococcus</i> spp. in field-collected zooplankton.

<p>Individual gut content (GC; prey ITS-1 copies ×10³ ind⁻¹) and size-specific gut content (ssGC; prey ITS-1 copies ×10³ µgWW⁻¹) in main zooplankton groups: copepods (adults and older copepodites of <i>Acartia</i> spp. and <i>Eurytemora affinis</i>), cladocerans (<i>Bosmina maritima</i> and <i>Podon</i> spp.) and microzooplankton (rotifers <i>Synchaeta</i> spp., <i>Keratella quadrata</i>, and <i>K. cochlearis</i>, and copepod nauplii). Data are shown as mean ± SD, number of samples is given below the group name.</p

Statistical summary of the generalized linear model examining effects of <i>Synechococcus</i> abundance (ITS-1 copies ×10³ ml) ⁻¹ and total phytoplankton (>2 µm) biovolume (mm³ ml⁻¹) in the water column (0–14 m) on the abundance of <i>Synechococcus</i> DNA in copepod stomachs (ITS-1 copies ×10³ ind⁻¹).

<p>Data are Box-Cox transformed, significant effects are in bold face.</p

Carbon uptake from ¹³C-labeled <i>Synechococcus bacillaris</i> by the copepod <i>Acartia tonsa</i> (live and dead individuals) exposed to the picocyanobacterium (Experiment III).

<p>Carbon uptake is expressed as change in δ¹³C of the copepods from the start values. Differences between the start and each treatment group are shown by asterisks (*: p<0.05; ***: p<0.0001). Data are shown as mean ± SD, <i>n</i> = 3 in all cases.</p