diff --git a/src/components/Card.tsx b/src/components/Card.tsx
index 4d39d2e..a5e9fff 100644
--- a/src/components/Card.tsx
+++ b/src/components/Card.tsx
@@ -35,7 +35,7 @@ export function Card({ children, full, className, tileId }: CardProps) {
   )
 }
 
-interface CardHeaderProps {
+export interface CardHeaderProps {
   dotColor: 'teal' | 'amber' | 'green' | 'alert' | 'purple'
   title: string
   rightText?: string
diff --git a/src/components/DetailPanel.tsx b/src/components/DetailPanel.tsx
new file mode 100644
index 0000000..12b854a
--- /dev/null
+++ b/src/components/DetailPanel.tsx
@@ -0,0 +1,229 @@
+import { useEffect, useRef } from 'react'
+import { X } from 'lucide-react'
+import { useDetailPanel } from '@/contexts/DetailPanelContext'
+import { useFocusTrap } from '@/hooks/useFocusTrap'
+import { DetailPanelContent } from '@/types/pmr'
+import type { CardHeaderProps } from './Card'
+
+// Width mapping from content type
+const widthMap: Record<DetailPanelContent['type'], 'narrow' | 'wide'> = {
+  kpi: 'narrow',
+  skill: 'narrow',
+  'skills-all': 'narrow',
+  consultation: 'wide',
+  project: 'wide',
+  education: 'narrow',
+  'career-role': 'wide',
+}
+
+// Title mapping from content data
+function getPanelTitle(content: DetailPanelContent): string {
+  switch (content.type) {
+    case 'kpi':
+      return content.kpi.label
+    case 'skill':
+      return content.skill.name
+    case 'skills-all':
+      return 'All Medications'
+    case 'consultation':
+      return content.consultation.role
+    case 'project':
+      return content.investigation.name
+    case 'education':
+      return content.document.title
+    case 'career-role':
+      return content.consultation.role
+  }
+}
+
+// Dot color mapping from content type
+function getDotColor(content: DetailPanelContent): CardHeaderProps['dotColor'] {
+  switch (content.type) {
+    case 'kpi':
+      return 'teal'
+    case 'skill':
+    case 'skills-all':
+      return 'amber'
+    case 'consultation':
+    case 'career-role':
+      return 'teal'
+    case 'project':
+      return 'amber'
+    case 'education':
+      return 'purple'
+  }
+}
+
+// Dot color value map (from Card.tsx)
+const dotColorValueMap: Record<CardHeaderProps['dotColor'], string> = {
+  teal: '#0D6E6E',
+  amber: '#D97706',
+  green: '#059669',
+  alert: '#DC2626',
+  purple: '#7C3AED',
+}
+
+export function DetailPanel() {
+  const { content, closePanel, isOpen } = useDetailPanel()
+  const panelRef = useRef<HTMLDivElement>(null)
+  const titleId = 'detail-panel-title'
+
+  // Focus trap when open
+  useFocusTrap(panelRef, isOpen)
+
+  // Close on Escape key
+  useEffect(() => {
+    if (!isOpen) return
+
+    const handleEscape = (event: KeyboardEvent) => {
+      if (event.key === 'Escape') {
+        closePanel()
+      }
+    }
+
+    document.addEventListener('keydown', handleEscape)
+    return () => document.removeEventListener('keydown', handleEscape)
+  }, [isOpen, closePanel])
+
+  if (!isOpen || !content) return null
+
+  const width = widthMap[content.type]
+  const title = getPanelTitle(content)
+  const dotColor = getDotColor(content)
+  const dotColorValue = dotColorValueMap[dotColor]
+
+  return (
+    <>
+      {/* Backdrop */}
+      <div
+        style={{
+          position: 'fixed',
+          inset: 0,
+          backgroundColor: 'var(--backdrop-bg)',
+          backdropFilter: 'blur(var(--backdrop-blur))',
+          zIndex: 1000,
+          animation: 'backdrop-fade-in 150ms ease-out',
+        }}
+        onClick={closePanel}
+        aria-hidden="true"
+      />
+
+      {/* Panel */}
+      <div
+        ref={panelRef}
+        role="dialog"
+        aria-modal="true"
+        aria-labelledby={titleId}
+        className="detail-panel"
+        data-width={width}
+        style={{
+          position: 'fixed',
+          top: 0,
+          right: 0,
+          bottom: 0,
+          backgroundColor: 'var(--surface)',
+          boxShadow: 'var(--shadow-lg)',
+          zIndex: 1001,
+          display: 'flex',
+          flexDirection: 'column',
+          animation: 'panel-slide-in 250ms ease-out',
+        }}
+      >
+        {/* Header */}
+        <div
+          style={{
+            display: 'flex',
+            alignItems: 'center',
+            justifyContent: 'space-between',
+            padding: '20px 24px',
+            borderBottom: '1px solid var(--border-light)',
+            flexShrink: 0,
+          }}
+        >
+          <div
+            style={{
+              display: 'flex',
+              alignItems: 'center',
+              gap: '8px',
+            }}
+          >
+            <div
+              style={{
+                width: '8px',
+                height: '8px',
+                borderRadius: '50%',
+                backgroundColor: dotColorValue,
+                flexShrink: 0,
+              }}
+              aria-hidden="true"
+            />
+            <h2
+              id={titleId}
+              style={{
+                fontSize: '14px',
+                fontWeight: 600,
+                color: 'var(--text-primary)',
+                fontFamily: 'var(--font-ui)',
+              }}
+            >
+              {title}
+            </h2>
+          </div>
+
+          <button
+            onClick={closePanel}
+            aria-label="Close panel"
+            style={{
+              display: 'flex',
+              alignItems: 'center',
+              justifyContent: 'center',
+              width: '32px',
+              height: '32px',
+              border: 'none',
+              background: 'transparent',
+              borderRadius: 'var(--radius-sm)',
+              cursor: 'pointer',
+              color: 'var(--text-secondary)',
+              transition: 'background-color 150ms, color 150ms',
+            }}
+            onMouseEnter={(e) => {
+              e.currentTarget.style.backgroundColor = 'var(--accent-light)'
+              e.currentTarget.style.color = 'var(--accent)'
+            }}
+            onMouseLeave={(e) => {
+              e.currentTarget.style.backgroundColor = 'transparent'
+              e.currentTarget.style.color = 'var(--text-secondary)'
+            }}
+          >
+            <X size={20} />
+          </button>
+        </div>
+
+        {/* Body (scrollable) */}
+        <div
+          style={{
+            flex: 1,
+            overflowY: 'auto',
+            padding: '24px',
+          }}
+        >
+          {/* Placeholder content - actual renderers will be added in later stories */}
+          <div
+            style={{
+              fontFamily: 'var(--font-ui)',
+              color: 'var(--text-secondary)',
+              fontSize: '14px',
+            }}
+          >
+            <p>
+              Detail panel for: <strong>{content.type}</strong>
+            </p>
+            <p style={{ marginTop: '8px', fontSize: '12px' }}>
+              Content renderers will be implemented in subsequent user stories.
+            </p>
+          </div>
+        </div>
+      </div>
+    </>
+  )
+}
diff --git a/src/contexts/DetailPanelContext.tsx b/src/contexts/DetailPanelContext.tsx
new file mode 100644
index 0000000..056e7e6
--- /dev/null
+++ b/src/contexts/DetailPanelContext.tsx
@@ -0,0 +1,52 @@
+import { createContext, useContext, useState, ReactNode } from 'react'
+import { DetailPanelContent } from '@/types/pmr'
+
+interface DetailPanelContextValue {
+  content: DetailPanelContent | null
+  openPanel: (content: DetailPanelContent) => void
+  closePanel: () => void
+  isOpen: boolean
+}
+
+const DetailPanelContext = createContext<DetailPanelContextValue | undefined>(
+  undefined
+)
+
+interface DetailPanelProviderProps {
+  children: ReactNode
+}
+
+export function DetailPanelProvider({ children }: DetailPanelProviderProps) {
+  const [content, setContent] = useState<DetailPanelContent | null>(null)
+
+  const openPanel = (newContent: DetailPanelContent) => {
+    setContent(newContent)
+  }
+
+  const closePanel = () => {
+    setContent(null)
+  }
+
+  const isOpen = content !== null
+
+  const value: DetailPanelContextValue = {
+    content,
+    openPanel,
+    closePanel,
+    isOpen,
+  }
+
+  return (
+    <DetailPanelContext.Provider value={value}>
+      {children}
+    </DetailPanelContext.Provider>
+  )
+}
+
+export function useDetailPanel(): DetailPanelContextValue {
+  const context = useContext(DetailPanelContext)
+  if (!context) {
+    throw new Error('useDetailPanel must be used within DetailPanelProvider')
+  }
+  return context
+}
diff --git a/src/hooks/useFocusTrap.ts b/src/hooks/useFocusTrap.ts
new file mode 100644
index 0000000..dda8a25
--- /dev/null
+++ b/src/hooks/useFocusTrap.ts
@@ -0,0 +1,80 @@
+import { RefObject, useEffect } from 'react'
+
+/**
+ * Focus trap hook for modal dialogs and panels
+ * Traps Tab/Shift+Tab within the container when active
+ * Returns focus to previously focused element when deactivated
+ */
+export function useFocusTrap(
+  containerRef: RefObject<HTMLElement>,
+  isActive: boolean
+): void {
+  useEffect(() => {
+    if (!isActive || !containerRef.current) return
+
+    const container = containerRef.current
+    const previousActiveElement = document.activeElement as HTMLElement
+
+    // Get all focusable elements
+    const getFocusableElements = (): HTMLElement[] => {
+      const selectors = [
+        'a[href]',
+        'button:not([disabled])',
+        'textarea:not([disabled])',
+        'input:not([disabled])',
+        'select:not([disabled])',
+        '[tabindex]:not([tabindex="-1"])',
+      ]
+
+      const elements = container.querySelectorAll<HTMLElement>(
+        selectors.join(', ')
+      )
+
+      return Array.from(elements).filter(
+        (el) => !el.hasAttribute('disabled') && el.offsetParent !== null
+      )
+    }
+
+    // Focus first element on mount
+    const focusableElements = getFocusableElements()
+    if (focusableElements.length > 0) {
+      focusableElements[0].focus()
+    }
+
+    // Handle Tab key to trap focus
+    const handleKeyDown = (event: KeyboardEvent) => {
+      if (event.key !== 'Tab') return
+
+      const focusable = getFocusableElements()
+      if (focusable.length === 0) return
+
+      const firstElement = focusable[0]
+      const lastElement = focusable[focusable.length - 1]
+      const activeElement = document.activeElement as HTMLElement
+
+      if (event.shiftKey) {
+        // Shift+Tab: moving backwards
+        if (activeElement === firstElement) {
+          event.preventDefault()
+          lastElement.focus()
+        }
+      } else {
+        // Tab: moving forwards
+        if (activeElement === lastElement) {
+          event.preventDefault()
+          firstElement.focus()
+        }
+      }
+    }
+
+    document.addEventListener('keydown', handleKeyDown)
+
+    // Cleanup: return focus to previous element
+    return () => {
+      document.removeEventListener('keydown', handleKeyDown)
+      if (previousActiveElement && previousActiveElement.focus) {
+        previousActiveElement.focus()
+      }
+    }
+  }, [isActive, containerRef])
+}
diff --git a/src/index.css b/src/index.css
index be85030..a6b8bac 100644
--- a/src/index.css
+++ b/src/index.css
@@ -423,6 +423,23 @@ textarea:focus-visible {
   to { opacity: 1; }
 }
 
+/* Detail panel responsive widths */
+.detail-panel[data-width="narrow"] {
+  width: var(--panel-narrow);
+}
+
+.detail-panel[data-width="wide"] {
+  width: var(--panel-wide);
+}
+
+/* Mobile: both narrow and wide become full-width */
+@media (max-width: 767px) {
+  .detail-panel[data-width="narrow"],
+  .detail-panel[data-width="wide"] {
+    width: 100vw;
+  }
+}
+
 @media (prefers-reduced-motion: reduce) {
   /* Disable pulse animation on status badge dot */
   @keyframes pulse {